To improve the dynamic performance degradation of spatial parallel robots caused by the lubrication clearance effect, an optimization method for spatial robot dynamics considering the lubrication clearance effect is proposed. A dynamics model of a 2-RPS-SPR spatial robot with lubricated spherical joint clearance is developed. Taking the rotational inertia of the end-effector and the dynamic viscosity of the lubricant as the design variable, the optimization model for parallel robot dynamics considering the effect of lubrication clearance is established. The dynamic optimization model is solved using Particle Swarm Optimization. The dynamic response characteristics of the robot are analyzed before and after optimization. Optimization results indicate that the dynamic optimization decreased the peak constraint reaction force at the spherical joint with lubrication clearance by 57.8N and 17.93N, and reduced the end-effector displacement error by 28.51% and 23.26%. This paper provides theoretical support for enhancing the dynamic performance of spatial robots by addressing the clearance effect.