Through the conventional low temperature performance test and Superpave low temperature performance test, the structural performance of different polyphosphoric acid(PPA) modified asphalt binder was investigated at low temperature, and the corresponding relationship of its performance evaluation index was analyzed. Further, the anti-cracking performance of asphalt mixture at low temperature was verified by the improved trabecular bending test and TSRST, and the correlation of low temperature performance between the asphalt binder and the mixture was studied. Finally, the rationality and deficiency of the evaluation index of different low temperature performance were analyzed. The results show that PPA reduced the ductility and stiffness modulus of asphalt, and the aging had great influence on the structural performance of PPA modified asphalt at low temperature. The strain energy density index shows that PPA can improve the cracking resistance of asphalt mixture at low temperature, the anti-cracking performance of PPA compound SBR modified asphalt was better than that of SBR modified asphalt, and the freezing temperature and freeze fracture strength can more accurately evaluate the low temperature performance of PPA modified asphalt.