In this paper, a crack analysis model based on finite element method and virtual crack extension technique was proposed to investigate the occurrence of surface fracture of polyethylene acetabular cup under gait loadings. To this, a simplified hip joint model was created for facture analysis. The stress intensity factor (SIF) at crack site was estimated and used to evaluate the propagation of the surface crack. Current results show that under normal gait loading, the SIF at crack tip within polyethylene cup was predicted to be lower than the fatigue threshold of polyethylene material. However, under the heel strike instant, the crack tip SIF exceeds the fracture strength of polyethylene subject to gamma radiation, which may drive the crack to propagate to final fracture. Overall, the presented analysis model has demonstrated the probability of severe surface damage occurring in polyethylene cup under impact walking conditions. This provides a valuable reference to the improvement of the mechanical properties or design of bearing materials in clinical orthopedic application.