The Theory of Six Kingdoms is the representative work of Su Xun's political theory. This paper puts forward and demonstrates the incisive argument that the downfall of the six countries is "blamed on Qin", criticizes the humiliating policy of the Song Dynasty towards Liao and Xixia, and warns the rulers of the Northern Song Dynasty to learn the lessons of the downfall of the six countries so as to avoid repeating the same mistakes. His sons Su Shi, Su Zhe and Li Zhen also wrote The Six Kingdoms in the Qing Dynasty, expounding their personal views.