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　asphalt,　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.