The dual structure of “secular power + religious authority” can be said to be the main feature of the Edo period. The “religious authority” referred to here is the theocracy born on the basis of Tokugawa Ieyasu’s legacy “Toushou Daigongen”. This paper discusses the establishment and social function of Edo theocracy under the influence of Tokugawa Ieyasu based on the original materials such as Junpuki，Shunkyuki，Tokugawajikki，etc. from the perspective of political ideology history and religious history. Through literature research，it is found that with the initiation of theocracy conception，Tokugawa’s religious belief in his later years gradually tilted from Pure Land Sect to Tendai Sect. Under his influence，the Edo Shogunate constructed the religious authority with the Samurai class as the object，the Toushou Daigongen. The combination of Toushou Daigongen and the secular power of Shogunate generals has become an important ideology of the political rule. However，this theocracy has gradually become an important part of Japanese folk beliefs besides being used by the Shogunate to rule warriors.