Sun Tzu's art of war should be produced after a long period of brewing. There are many factors that cause it, so we should choose the following points: China's frequent, intense and diverse wars since ancient times, especially in the Spring and Autumn Period, are the source of Sun Tzu's Art of War; Previous theoretical achievements of military science, such as military annals, military and political affairs, ancient Sima Fa, Lingdian, etc. It is a stepping stone for Sun Tzu's Art of War to leap to the peak of military science. The social ideological trend in the Spring and Autumn Period, especially the doctrines of "Tao", "Benevolence", "Yin and Yang" and "Protecting the People" are the cultural factors for the formation of Sun Tzu's Art of War. Qi culture, which worships the wise and wise, is a fertile ground for cultivating Sun Tzu's Art of War, a wonderful military theory. Sun Wu's personal talent and efforts are the subjective factors of Sun Tzu's Art of War. In addition, the thinking modes of the Chinese nation, such as holistic thinking, dialectical thinking and image thinking, formed in the pre-Qin period have played a guiding role in the construction of the theoretical system of Sun Tzu's Art of War. This is the main reason why The Art of War came into being in China rather than abroad, and in the Spring and Autumn Period rather than other periods.