Abstract: TC4 titanium alloy plates were subjected to laser shot peening for different times and then subjected to high cycle fatigue tests. The fatigue properties and fracture mechanism of the alloy were studied. Considering the retardation effect of the residual compressive stress and the mesoscopic size of grain boundaries on the microcrack growth, the suppression parameter, open stress intensity factor and residual stress intensity factor were introduced to modify the Paris formula. Then a prediction model for fatigue microcrack growth after laser shot peening was established and verified by experiments. The results show that with the increase of the number of shot peening, the fatigue strength and fatigue life of the TC4 titanium alloy increased, and the fracture mode changed from brittle fracture to ductile fracture. The relative errors of the fatigue life predicted by the fatigue microcrack prediction model and the test results were less than 10%, indicating that the model was accurate.