Abstract The high-temperature storage stability of styrene-butadiene-styrene 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.