Abstract: This is an article in the field of ceramics and composites. In order to explore a new way for the application of phosphogypsum in road materials, phosphogypsum powder and asphalt mortar were mixed to prepare phosphogypsum modified asphalt. The effects of mixing temperature, powder-binder ratio and polyphosphoric acid content on the three major indicators of phosphogypsum modified asphalt were studied. The research results show that the softening point increases as the mixing temperature increases, and the ductility increased first and then kept constant. Considering energy efficiency and aging temperature, the processing temperature of asphalt should be in the range 135 °C and 145 °C. increasing the powder gum ratio can increase the softening point of the modified asphalt and decrease the ductility of the asphalt. Therefore, the ratio of filler bitumen should not be greater than 0.9 using phosphogypsum as the modifier. The addition of polyphosphoric acid greatly increases the softening point of modified asphalt, but reduces its ductility and penetration. The optimal amount of polyphosphoric acid should be around 1.5%. Infrared spectroscopy (FTIR) and thermogravimetric analysis (TG-DSC) showed that phosphogypsum physically functioned with Asphalt. When polyphosphoric acid was mixed into asphalt, it would react chemically with asphalt. The research results could provide references for the engineering application and theoretical research of phosphogypsum in road materials.