A modified asphalt waterproof coatings was prepared by using acrylic emulsion and emulsified asphalt as raw materials，different fineness of heavy calcium carbonate（GCC）and granulated blast furnace slag（GS）as inorganic filler，and adding defoamer，thickener and other additives. In order to explore the effect of GCC/GS composite on the performance of modified asphalt waterproof coatings，the effects were analyzed by measuring the tensile properties，bonding strength，water absorption and low tenderness of the coating with different fineness in different environments，and the influence of the fineness and content of GCC/GS on the performance of waterproof coatings was analyzed. At the same time，the surface morphologyof the coatings prepared with different fineness of GCC and GS mixed in different proportionswas observed by scanning electron microscopy（SEM）. The results showed that the fineness and double blending ratio of GCC/GS had a significant effect on the performance of themodified asphalt waterproof coatings，and the coating performance was better when 600 GCC-A was double-mixed with S95 grade GS-A and w（GS）=12%.