In order to further reduce the drilling difficulty of infill adjustment wells in the Fuling Shale Gas Field， as well as improve the drilling speed， research on infill well trajectories optimization design has been carried out in regard to the geological characteristics of the shale gas field. The 3D trajectory design for shale gas drilling mainly includes three types：“fivepoint sixsection” trajectory， “sixsection with the circular arc in the inclined plane” trajectory and “dual2D” trajectory. The optimized “circular arc in the inclined plane” 3D trajectory is determined to be more suitable for horizontal well design in the Fuling Shale Gas Field by comparison of the indicators such as the length of directional section， drag force， torque. To optimize the parameters of the 3D trajectory design with circular arc in the inclined plane， a case study has been conducted on trajectory optimization design for a 3D horizontal well with the kick off point and buildup rate optimized through comparison of drag force and torque at different kick off points and buildup rates to find out the minimum drag force and torque. It can provide reference for the infill well trajectory optimization design in the Fuling Shale Gas Field．