Abstract:This article starts with the special points of the name and shape of Dongzhimen and Xizhimen in Beijing in the Ming and Qing Dynasties. It tries to find the direct cause of its existence and the basis of the deep ritual system. After combing the institutional inheritance relations between the Ming and Qing dynasties of Beijing, Yuan Dadu, Jinzhongdu, and the Northern Song Dynasty, the concept of " System of Main And Straight Entrance " in the gate system of the ancient Chinese capital Wengcheng City was proposed: the city's four main entrances are straight gates. The Wengcheng plane has a square shape and intersects at right angles on both sides of its front end.