Cluster well platform mode is one of the important means to develop shale gas vigorously. However, due to the small distance of cluster platform wells, the risk of collision between current wells and adjacent wells is high, and the anti-collision design of wellbore trajectory is difficult. The conventional well trajectory design method is to first design the trajectory and then analyze anti-collision until the anti-collision index is met. A lot of trial calculation is required, which consumes manpower. The theory of well trajectory error analysis was proposed to calculate the key parameters of trajectory that meet the requirements of anti-collision, so as to improve the efficiency of cluster well trajectory design. The influence factors of the key parameters of the track were analyzed by using ISCWSA error model. The results show that the critical anti-collision depth of the parallel wellbore above the well trajectory of cluster well is closely related to the wellhead spacing, and the critical depth increases with the increase of the wellhead spacing. The position of the kickoff point must be less than the critical depth of anti-collision, and proper advance kickoff is conducive to anti-collision. The advance of the position of the kickoff point is related to the build-up rate. Increasing the advance of the kickoff point can reduce the requirements for the build-up rate of the kickoff point. At the same time, the calculation models of anti-collision critical depth of parallel wells, critical build-up rate of kickoff point, advance of kickoff point and critical angle of inclination of stable section are established, which provides a theoretical means for quickly designing the well trajectory meeting the anti-collision requirements.