The work aims to improve the fatigue life of AerMet100 steel by studying the effect of shot peening on surface integrity and fatigue properties of AerMet100 steel. The surface integrity test was used to analyze the effects of shot peening on surface morphology, roughness, grain size, hardness, residual stress and microscopic structure and fatigue test was carried out to observe fatigue fracture morphology observed and analyze the effect of shot peening on fatigue performance. After shot peening, the surface of the sample had obvious plastic deformation, the roughness was increased, the grain size was refined, the hardness was increased, and the residual compressive stress layer of about 140 μm was formed. After the shot peening, staggered martensite laths were formed, and the dislocations in the strengthening layer were increased to produce refined martensite laths and twins. In the fatigue test, the mean life of the sample before shot peening was 163 566 cycles, the mean life of the sample after shot peening was 209 552 cycles and the average increase was 28.1%. After shot peening, there were many crack sources on the fracture surface of the sample, and the crack propagation path was twists and turns, resulting in uneven steps at the edge of the fracture surface, which consumed more energy. The overall morphology of the crack growth zone in the strengthened layer of the sample was jumble and disorder, and the fatigue band was finer than that of the sample before shot peening, which indicated that the crack growth rate was slower. The fatigue resistance of AerMet100 steel after shot peening is increased, and the fatigue life is significantly improved.