The work aims to clarify the influence mechanism of shot peening intensity on fatigue life of 316 stainless steel. After chemical corrosion, the change of microstructure of 316 stainless steel subjected to shot peening with different intensity was observed by optical microscope. Then the changes in surface profile, surface roughness, microhardness and residual stress before and after shot peening were analyzed by white light interferometer, digital vickers microhardness tester and X-ray residual stress analyzer respectively. The tensile properties and fatigue life before and after shot peening were also measured by fatigue testing machine. After shot peening, the surface roughness of the specimens increased obviously and Sa value increased from 0.04 μm to 6.73 μm with the increase of peening intensity. In addition, shot peening produced a microstructural gradient from the near surface region to the bulk material with the total thickness of the near surface deformed layer lying between 110 μm and 290 μm, which was dependable on the peening intensity. During shot peening, work hardening occurred and a certain depth of residual compressive stress layer was introduced. By increasing the peening intensity, the maximum microhardness and compressive residual stress augmented from 356HV0.1 to 435HV0.1 and from -633 MPa to -750 MPa, respectively. Compared with the un-peened specimens, shot peening improved the behavior and properties of the peened specimens. The plastic strain amplitude was decreased, but the fatigue lifetime of peened specimens was increased. Shot peening can effectively improve the comprehensive mechanical properties of 316 stainless steel and increase its fatigue life. The effect of shot peening with different intensity is obviously different. When the shot peening intensity is 0.35 mmA, the best shot peening effect is achieved.