Abstract: To obtain mechanical parameters of semi-rigid base asphalt pavement and analyze the variation law of mechanical parameters,large-scale asphalt pavement structure of semi-rigid base was designed and constructed in laboratory test tank to carry out structural internal stress,strain and modulus layered detection and experiment by stepwise loading method.Based on detection and experiment data,the 3D finite element model of road is set up.On the basis of model validation,numerical simulation of bearing plate test is carried out.The problems of crack initiation location,crack initiation load,crack status,stress intensity factor and crack type for reason of overloading are analyzed.The results show that cracks begin to appear when the traffic load exceeds the crack initiation load of semi-rigid base.The units which are along transverse direction of the base layer bottom of pavement and close to the centre axis line of the bearing plate crack first.Then cracks further extend up to the surface to form transverse cracks of base layer by the effect of traffic load.The cracks of semi-rigid base caused by load are mainly tensile cracks of type I.The value of stress intensity factor depends on the applied load size,crack length and model geometry.So measures should focus on the aspects of reasonable thickness design of base,improved performance of base material property and strict control of overloading to reduce formation of semi-rigid base cracks.