Abstract: The warm-mix flame retardant composite modified asphalt was prepared with warm-mix agent（Sasobit）, aluminum hydroxide（ATH）, organic montmorillonite（OMMT） and base asphalt, and fourier transform infrared（FTIR） scanning, thermogravimetric（TG） analysis and differential scanning calorimetry were used to investigate the coordination and synergistic effect of warm-mix agent and flame retardant and the flame retardant mechanism. The results show that the modification effect of warm-mix agent and flame retardant on the base asphalt is mainly physical modification. The addition of flame retardant can improve the thermal stability, flame retardant and smoke suppression effects of asphalt, and the flame retardant, smoke suppression effects are improved with the increasing of the amount of flame retardant. The flame retardant can form barrier coating on the asphalt surface with wrapping effect, which can effectively reduce the heat flow rate with excellent flame retardant efficiency and combustion process control ability. The compounded flame retardants of ATH and OMMT can provide the synergistic flame retardant effect, and the flame retardant mechanisms are mainly heat exchange interruption and condensed phase flame retardant. When the compounded flame retardant content is 8%, the asphalt has good flame retardant and smoke suppression properties with good economy.