Simply put, the decline of science and technology was in the Ming Dynasty after the Yuan Dynasty. Because in the Song Dynasty, China's science and technology were very developed. Especially in the field of neo-Confucianism. But then the Yuan Dynasty replaced the Song Dynasty. Genghis Khan was originally a grassland hero. He led his people to capture the Song Dynasty in order to thoroughly understand the traces of the Song Dynasty. The first is cultural cleanup. In this way, the knowledge of Neo-Confucianism, which was finally developed in the Song Dynasty, declined again. Then in the Ming Dynasty after the Yuan Dynasty, because of Zhu Yuanzhang's autocracy, culture declined again. The economic downturn mainly started when foreign countries imported opium to China for the second time. He changed the profitability of China's foreign trade. China's economy began to decline. Coupled with the Qing government's self-interest in its own country. The adoption of the "closed door" policy made it impossible for the outside world to understand, which eventually led to a great economic downturn. These are the main points.