Abstract: The effect of roll Press strengthening on the fatigue fracture of bolts which made of 30CrMnSiNi₂A steel was studied. The experimental result shows that the endurance limit of the bolts is increased about 58.6% by roll press strengthening, the fatigue fracture appearane is changed, the number of the origin region of the fatigue crack is reduced, the area of the crack growth zone is increased, and the width of the fatigue striahon is decreased. Finely, the mechanism of roll press strengthening was discussed.