The invention relates to an application of rice hull ash as an asphalt modifier. The test of three indexes of asphalt, the Bush rotary viscosity test and the DSR (dynamic shear rheometer) test prove that the rice hull ash asphalt modifier can effectively improve high-temperature deformation resistance and durability of asphalt cement and an asphalt mixture and guarantee certain low-temperature crack resistance. Therefore, diseases of asphalt pavements in high-temperature regions are effectively reduced, the asphalt pavements can adapt to complicated and changeable environmental conditions, and driving safety and service level are guaranteed. Besides, the microwave heating test and infrared thermal imaging photographing prove that compared with limestone mineral powder filler, the rice hull ash asphalt modifier enables the modified asphalt mortar to have an obviously higher microwave heat absorption temperature-rise rate, so that the rice hull ash asphalt modifier can be applied to technical research of the field of ice and snow smelting for the asphalt pavements.