The invention relates to a preparation method of a p-aramid fiber-mica paper. The preparation method comprises defibering and dispersing silane coupling agent-modified p-aramid chopped fibers to obtain slurry A, carrying out screening on the p-aramid fibrids with a beating degree of 40-65 degrees SR to obtain slurry B, modifying mica plates through an ionic starch solution to obtain modified mica plates, mixing the slurry A, the slurry B and the modified mica plates to obtain uniform mixed slurry, wherein the uniform mixed slurry comprises, by mass, 10-20% of p-aramid chopped fibers, 20-40% of the p-aramid fibrids and 40-70% of the mica plates, carrying out sizing, dehydration and formation on the mixed slurry, carrying out squeezing and drying and carrying out hot press molding to obtain the p-aramid fiber-mica paper. The p-aramid fiber-mica paper obtained through fiber screening and modification, wet method paper making and hot pressing molding has good evenness, excellent mechanical strength, excellent dielectric breakdown strength and high temperature resistance stability.