The high-temperature storage stability of styrene-butadienestyrene triblock copolymer (SBS) modified asphalt can be improved to some extent with the addition of phosphorus trichloride. The dynamic mechanical and physical properties of SBS modified asphalts before and after adding phosphorus trichloride were studied respectively. The addition of phosphorus trichloride to asphalt improved the high-temperature performance of asphalt and reduced its temperature susceptibility to a great extent with unfavourable effect on low-temperature ductility. The addition of SBS to phosphorus trichloride modified asphalt increased the low-temperature ductility, viscosity of asphalt and improved its high-temperature performance further. Different SBS structures influenced the rheological and physical properties of asphalt before and after adding phosphorous trichloride.