To prevent shear fracture or excessive permanent deformation of the asphalt concrete function layer in cement concrete pavement under vehicle loads, the self developed accumulative deformation test device was adopted to study the shearing deformation properties of function layer asphalt concrete under repeated loads. The influence factors of permanent deformation were analyzed using grey relation analysis. Results show that the accumulated deformation test device of functional layer can simulate the practical stress state of function layer reasonably and the cumulative deformation of function layer rises in the form of logarithmic curve. Deformation and warping happen to the specimens when the cumulative deformation is smaller than 30mm, while crushing and fracture are generated in the specimens with the cumulative deformation is larger than 35mm. Asphalt content has the most important effect on the accumulated deformation of asphalt concrete function layer, followed by aggregate gradation and void ratio. The lateral extrusion deformation of the specimen is greater than the decrease of volume due to compaction effect. Therefore, the main reason of the accumulated deformation of asphalt concrete function layer is the shearing action of the panel near the joint, rather than the compaction effect.