Based on finite element method, the analysis method of static strength and fatigue strength of connecting bolt on the main drive system of a MW wind turbine was studied. The mechanical model of the drive chain system was simplified and the finite element model of the drive chain system was established. According to GL regulation, the static strength and fatigue strength of the bolt were calculated, and the sensitivity difference of the external load component influence on the bolt force was fully considered. In addition, the force characteristics of the drive chain connecting bolt and the influence of external load on the bolt strength calculation were analyzed according to the calculation results. The research results provide reference for the accurate calculation of the strength of connecting bolt in wind power system.