Halogen-free flame retardant phosphoric epoxy resin formula for copper-clad laminate was studied and prepared at the conditions of glass fiber cloth as base material, dicyandiamide as curing agent and 2-methyl iminazole as accelerating agent. According to the experiment results, the optimal formula for copper-clad laminate was epoxy resin(E-2145) 159.8 g with 2.5 % mass percent phosphorus，dicyandiamide 4 g，2-methyl iminazole 0.06 g，aluminum hydroxide accounting for 20 % mass percent in the whole formula system and acetone 1.2g.