Aiming at the current situation that the stiffness performance of wheel bearing units will directly affect the service performance of automobiles,the stiffness characteristics of wheel bearings are investiga-ted,and a method based on the analysis of dynamic stiffness characteristics of non-standard wheel bearings by Romax and an design method based on particle swarm algorithm(PSO)are proposed.By using Romax software to simulate the non-standard wheel bearings,the influence of preload,contact angle and two-row spherical centre distance on the dynamic stiffness matrix of a certain type of wheel bearings is investigated and verified by theory and test.The results show that:with the increase of preload,the dynamic stiffness of the bearing shows an overall increasing trend;with the increase of contact angle,the radial stiffness decrea-ses,and the axial stiffness and angular stiffness increase;with the increase of the two rows of ball distance,the radial stiffness and axial stiffness decrease slightly,and the angular stiffness increases.Taking the maxi-mum angular stiffness of the wheel bearing unit as the optimization objective,the internal structural parame-ters of the bearing are optimized and designed,and the angular stiffness increases by 14.4%after the opti-mization,which achieves the optimization objective of increasing the angular stiffness,and provides meth-odological support for the design and optimization of the wheel bearing structure.