Abstract: To address the limited operational stability of grid-forming wind turbine generators under complex multi-wind-speed operating conditions and the inaccurate stability evaluation resulting from neglecting prime mover dynamics (leading to the omission of oscillation modes), this paper proposes a multi-operating-condition parameter collaborative optimization method considering prime mover dynamics. Firstly, a full-order small-signal model covering the aerodynamic, mechanical, electrical and control loops is established, and comparative models with and without prime mover dynamics are constructed. Combining the state-space method and the complex torque coefficient method, the key effects of prime mover dynamics on system stability are revealed at the mechanism level. Secondly, based on on the results of dominant oscillation mode identification, an improved multi-objective particle swarm optimization algorithm is proposed, introducing parameter sensitivity factors to guide optimization and integrate physical model characteristics. PSCAD/EMTDC simulation results demonstrate that the proposed method can effectively improve the system stability margin and dynamic response performance, providing a reliable basis for the multi-operating-condition stable operation and parameter design of grid-forming wind turbine generators.