Abstract: To carry on fatigue analysis and structural optimization for spring-seat lower of strut assembly, the finite element model of spring-seat lower was set up. On the basis of quasi-static finite element fatigue analysis, the fatigue life of spring-seat lower was predicted by the way of emulation. Meanwhile, the structure of spring-seat lower was optimized. The correctness of fatigue simulation analysis is verified by fatigue bench test and crack fracture analysis.