Abstract: This paper studied the interactional mechanism of the microstructure of diatomite and asphalt by the test of scan electronic microscope and DSC.It is pointed that the diatomite can uniformity distributing to as- phalt,and form stabilization system with asphalt.The especially microstructure for diatomite can absorb the oil of asphalt,and help to improve the performance of road;it was not only the use of filling,even more the modified use for the asphalt,the results indicate that diatomite-modified asphalt improve stability of both high temperature and low temperature which offered the theory warrant to the application of the diatomite-modified asphalt.