China first used seawalls for military purposes in the Jin Dynasty. The Jin Dynasty was the beginning of seawall construction in China. The first seawall appeared in the Xianhe period of the Eastern Jin Dynasty (AD 326-334) and was named "seawall prevention". "Lei" is the original name of seawall. It was built by Wushi Yutan in the front of the Yangtze River Delta. At this time, the purpose of construction is to prevent moisture. More than half a century later, in 400 AD, China began to build seawalls for military purposes. At that time, a peasant uprising led by Sun En and Lu Xun broke out. Insurgents occupied Zhoushan Islands and frequently attacked the southeast coastal areas. Facing the attack of the rebel army, the rulers of the Eastern Jin Dynasty thought of the seawall and quickly built it into a defensive fortress. According to the Book of Jin Lu Biography, there was a history in Yuan Dynasty that Wu "built a base to be arrogant and prepared for going to sea", and there was another saying: "Build a thief and desecrate the base to prevent pirates." The "recklessness" in this article refers to the present Shanghai area. "En" is Sun En, the leader of the peasant uprising in the Eastern Jin Dynasty. Later, "Haikou" also refers to the maritime insurgents led by Sun En. Although Yuan quickly wiped out the insurgents in Hudu, the seawall defense he created had a great influence on the military struggle of the insurgents. From this period of history, we can also see that shortly after the birth of seawall, people discovered its national defense value and put it into practice.

In the era of cold weapons, seawalls have a very obvious defensive effect on attackers who use bows and arrows. Therefore, many rulers in the past dynasties attached great importance to its national defense function when building seawalls, and built seawalls high and firm. For example, in the Southern Song Dynasty, the main road of Xiaozong (A.D.11173) built a seawall, starting from Laohezui in Jiading in the north and reaching the west of Ganpu in Haining in the south, which is higher than the city wall, and has a good military defense function. To this end, the world commented that "coastal defense is impregnable." Its effectiveness in national defense is evident from this.

When the Japanese invaders attacked at the end of the Yuan Dynasty, people of insight put forward the defense method of building seawalls in the south to the north. For example, Yu Ji, a famous scholar at that time, said: "To the east of the capital, thousands of miles away from the sea, three seas in the Arctic, Qingqi in the south and Weitian in the south; And when the tide comes, silt is fertile soil. It is advisable to use Nanren method to build dikes, defend water for fields, recruit rich people to cultivate, and collect taxes for three years, which can protect the capital, prevent island loss and save shipping. " In the 12th year of Zheng Zheng (A.D. 1352), Tuotuo became the phase, which was vigorously promoted because of the theory of Zong Qi, but it didn't recover for a long time for various reasons (Volume 11 of Reading Historical Records). "Shimayi" in the article refers to Japanese pirates. Although this proposal was not successfully implemented, it reflected that the ancients understood the dual functions of seawalls and hoped to apply them to the northern region to strengthen the defense of important places in the capital.

In the Ming Dynasty, due to the attention of the rulers, the seawall was overhauled 13 times in just over 270 years, which initially laid the foundation for today's seawall. At this time, the technology has also been greatly improved. Basically, it is built with huge stones and the structure is reasonable. After Jiajing in the Ming Dynasty, the Japanese invaders were rampant, and the seawall of Changgu in Wan Li became an important fortification for the broad masses of soldiers and civilians along the coast to fight against the Japanese invaders. In this regard, the Ming people and some later works specializing in coastal defense or seawall have pointed out. For example, "Lin Yan in Salt Town" says: "The seawall in Haiyan area is moisture-proof; If you refuse to face the pond, you can resist the invasion of Haikou. The pond is surrounded by fertile fields and rich rooms facing fireworks. The person who relies on it is just a pond. " "The Picture of Coastal Defence" says: "The coastal defence pond is as high as a wall, with a harbor for protecting the pond, which is four feet wide and one foot and five feet deep. It was used by the Ming Dynasty to defend against bandits. " Another article, An Examination of Seawalls, said: "The seawall system is higher than the city wall, and the inner and outer ponds and ditches are sandwiched together. Soup and coastal defense are solid and also used to prevent the sea, so the planning is particularly advocated. " Later historical materials also show that General Tanghe brought seawalls into his defense system as an important part of coastal defense as early as the early Ming Dynasty, which was highly praised by the Ming people.