At present, the azimuth drift often occurs in the drilling process of deep shale gas horizontal wells, which seriously affects the trajectory control of the horizontal well, and then affects the accurate target of the horizontal well. In the field construction in this area, usually according to the previous drilling experience, an “advanced azimuth angle” should be estimated before the directional slanting is carried out, but there are a lot of uncertainties in this field practice and there may be some big error. In this paper, a method of horizontal well trajectory optimization design based on azimuth drift is proposed, which solves the inaccuracy of “advanced azimuth angle” only estimated by the field experience. The optimization design of horizontal well trajectory is devided according to the well sections; the average azimuth drift rate of the well section is obtained by combining the stratigraphic factors with the well profile. Based on this method, the software for the optimization design of horizontal well trajectory based on azimuth drift is developed. The feasibility of this method is proved by the examples.