Abstract: In order to solve the main problems about high toxicity, expensive cost and poor thermostability of asphalt flame retardants currently, two types of new inorganic composite flame retardants consist of metallic oxide and metal hydroxide were prepared. The high temperature rheological properties, low temperature rheological properties and the viscosity characteristics of the two types of new flame retardant modified asphalts were studied deeply through dynamic shear rheological test, bending beam rheological (BBR) test and Brookfield rotational viscosity test. On this basis, the flame retardant mechanisms of the two types of flame retardant modified asphalts were studied using DSC, and the economic benefits of the two types of flame retardants were compared with the flame retardants in common use. Results show that the effect of restraint smoke of the two types of inorganic composite flame retardants is good, the high temperature rut resistance and the viscosity of the asphalts can be improved, and the low temperature performance of asphalt mastic can be strengthened significantly by the two types of flame retardants. The rut resistance factor of the two types of flame retardants shows good correlation with temperature. The incorporation of the two types of flame retardant makes the asphalts require more energy in phase changing, and modified asphalts are more stable in heating process at high temperature.