During the Three Kingdoms period, years of warlord melee caused serious damage to iron smelting. Iron is so scarce that it appears that the coffin is cut to get nails, and wooden instruments of torture are used instead of iron instruments of torture (leg pliers). After Cao Cao occupied Hebei Province, he began to resume the iron smelting business, set up an official smelting and casting institution, appointed Wang as the governor, and Han Ji as the smelting and casting supervisor, in charge of smelting and casting matters. Han Ji pays attention to adopting new technology, improving the original drainage system and popularizing it.

Due to the extensive use of drainage pipes, the iron smelting industry developed in the Three Kingdoms period, which improved the output and quality of iron, greatly increased the quantity and quality of iron, and was more conducive to the recovery and development of agricultural and handicraft production. Due to the recovery and development of agricultural handicrafts, commodity exchange has also improved. A five-baht (then common currency) strike took place in Wei Wendi, and Wei Mingdi officially resumed, which changed the situation of barter in the past. This promoted the economic recovery of the Central Plains, helped to maintain the unification of the north, supported the Wei and Jin wars against Shu and Wu, and laid a material foundation for the destruction of Shu and the unification of China.