The invention discloses a torsional vibration optimization method for a planetary series-parallel hybrid power system, and aims to solve the problem of complex torsional vibration of a planetary series-parallel hybrid passenger car caused by increase of a power source and change of a working mode and a working mode of a planetary gear mechanism. The method comprises: establishing a centralized mass model of a transmission component through the D'alembert principle and the Lagrangian equation, a matrix equation of the whole vehicle is further determined, and the modal shape of each mode is determined based on the inherent frequency; utilizing a modal participation factor theory to research the main participation modal of forced vibration of the component; based on parameter sensitivity analysis, determining an influence rule of parameter change on the inherent frequency and the resonance peak value. With the optimization of the inherent frequency of the transmission system and the reduction of a resonance peak value as evaluation criteria, the torsional vibration optimization design of the transmission system is realized. The complex torsional vibration analysis optimization methodfor the planetary series-parallel type passenger car structure is systematically provided, and a powerful theoretical basis is provided for researching complex torsional vibration characteristics of the planetary series-parallel type passenger car.