Differential steering of in-wheel electric vehicle provides the functions of both active steering and power assisted steering with the coupling control of force and displacement transfer characteristic of system. A collaborative optimization model of the differential power-assisted steering system of in-wheel electric vehicle is built, with steering economy as the main system optimization goal, steering road feel, steering sensitivity and torque sensor performance as the subsystem optimization goals. Considering the coupled relationship of each discipline, the main system is optimized by the particle swarm algorithm, and the subsystems are optimized by the directional heuristic search algorithm which is good on local optimization. The simulation results show that the collaborative optimization based on particle swarm algorithm has more optimal solution sets and fast convergence by considering the coupling relationship between different disciplines, and the comprehensive performance of in-wheel electric vehicle is improved.