In northern China, pavement cracking often occurs due to low temperature. To solve this problem, dioctyl phthalate(DOP) plasticizer was mixed into SBS modified asphalt to improve the low temperature resistance of asphalt. This experiment was carried out under the condition of equal penetration, the optimum dosage of plasticizer was determined and the road performance of asphalts and asphalt mixtures was compared. The results show that the plasticizer greatly increases the asphalt ductility and penetration, decreases the softening point and viscosity. The plasticizer reduces the high temperature stability and improves the low temperature performance of asphalt mixtures. The plasticized SBS modified 90# asphalt mixture is the best in anti freezing cracking performance.