In order to explore the development law of reflection cracks in semi-rigid pavement under traffic load and the stress change trend under different crack morphologies, the stress intensity factor is used as the characterization object of crack stress intensity, and the change of stress intensity factor in the process of load movement is studied by changing the angle, length and traffic load of inclined crack. The results show that: 1) The open stress intensity factor K_I decreases with the increase of the inclination angle of the reflection crack and the traffic load, and the peak value of K_I decreases by 33.74% when the inclination angle increases from 0° to 30°; and the trend of shear stress intensity factor K_II? is opposite, and the peak value of K_II? increases 90.7% with the increase of inclination angle to 30°. 2) When the inclination angle is 30°, both K_I and K_I increase with the increase of crack length. Lateral comparison shows that K_I is more significantly affected by crack length. Under the same crack length, the growth rate of K_I? is about 32% higher than that of K_II? ; 3) In the process of increasing traffic load, the peak value of K_I increases from 0.235 MPa·m^1/2 to 0.375 MPa·m^1/2, an increase of 59.6%, and the comprehensive stress intensity factor is proportional to the traffic load. The research results have certain engineering application value for the reasonable evaluation of cracks in semi-rigid pavement structures and the maintenance and disposal of reflection cracks.