[Purposes] This study aims to investigate the performance of styrene-butadiene-styrene block copolymer (SBS) and polyurethane (PU) composite modified asphalt mixture. [Methods] The composite modified asphalt was prepared by 2.0% SBS and PU with different dosages (4.0%, 6.0% and 8.0%), and modified asphalt was used to produce the dense-graded asphalt mixture AC-13. The high-temperature rutting resistance, low-temperature crack resistance and water stability of the asphalt mixture were evaluated by Marshall test, rutting test and low-temperature bending creep test were performed, and the modified asphalt mixture with 4.0% SBS and 6.0% PU was set as the control group. [Findings] SBS/PU composite modified asphalt mixture can meet the road performance requirements for asphalt pavement. Among them, the dynamic stability of 2.0%SBS+6.0%PU composite modified asphalt mixture was 144%, 19% and 52% higher than that of matrix asphalt mixture, 4.0% SBS modified asphalt mixture and 6.0% PU modified asphalt mixture, respectively. The high temperature stability of SBS/PU composite modified asphalt mixture was improved compared with that of the control group, and the water stability was comparable to that of the control group, and the improvement effect on low temperature performance was not obvious. [Conclusions] Considering the modification efficiency and economical efficiency, the optimal content of SBS/PU composite modified asphalt mixture is 2.0%SBS+6.0%PU.