Flame retardant asphalt was prepared in the form of ZnMgAl CO3 LDHs. The thermogravimetry differential scanning calorimetry, cone calorimeter and X ray photoelectron spectroscopy were used to investigate the effects of layered double hydroxides(LDHs) on the flame retardancy and smoke suppression performance of asphalt. The flame retardant mechanism of LDHs was further analyzed. The results show that 2% LDHs can reduce the maximum heat release rate, average heat release rate and total smoke release of asphalt combustion by 249%, 143% and 270% respectively. It shows better effects on flame retardant and smoke suppression with 2% LDHs, while limited effects on performance boost with 25% LDHs. The layered structure of LDHs can reduce the weight loss rate of asphalt in the initial stage of asphalt combustion and improve the integrity, compactness and oxidation resistance of combustion residues, but the thermal desorption mechanism of LDHs does not play a significant role in the process of asphalt combustion.