1. People-oriented, reducing people's burden. Through the peasant uprising at the end of Sui Dynasty, the Tang Dynasty fully realized the power of the people. In this way, when Li Yuan unified the Guanzhong area, he implemented a policy of recuperation, which continued after Emperor Taizong ascended the throne. Similar to the period of Emperor Wen and Emperor Jing in the early Han Dynasty, the policy of "governing by doing nothing" was implemented, partly because Li claimed to be Lao Zi, so he adopted a policy of recuperation in governing the country. Some people upstairs say that there is nothing wrong with the idea of "people-oriented", but it is different from today's "people-oriented", but Tang Taizong realized the power of the people and had a sense of awe.

2. Adopt lenient laws, especially the death penalty, requiring five repetitions in two days, paying attention to human life, and abolishing many cruel corporal punishments, such as amputation of hands and feet.

3. Politically, the idea of advocating the rule of the monarch and his subjects. Li Shimin believes that the monarch is not the only monarch in the world, and both the monarch and his officials should be responsible for the rise and fall of the country. The monarch can't act arbitrarily, just like Emperor Yang Di, he has the will to power, which is unique to me.

4. Advocate remonstrance and let courtiers speak freely. Li Shimin realized that no one is perfect, even the emperor can't always make accurate judgments, so he advocated that courtiers give more suggestions and don't be afraid of self-contradiction. It takes a broad mind to do this.

5. Enlightened ethnic policy. During the Zhenguan period, Emperor Taizong was admired by the neighboring minority regimes and called him "Tiankhan". Allow tribal leaders to continue to command the land and people, influence them with China's advanced culture, and let them actively integrate into the Chinese nation.

6. Improve the imperial examination system. Li Shimin perfected the imperial examination system established by Emperor Wendi of Sui Dynasty, which made the ruling class pay more attention to talents instead of family status, which undoubtedly promoted the development of history.

You can refer to these two books: The Biography of Emperor Taizong (Xu Daoxun, Zhao Edition) and A Review of Li Shimin.