The invention relates to a preparation method of epoxy mortar. The preparation method comprises the following steps of: uniformly mixing 5-7 parts of 1-bromo-1-phenyl ethane and 4 parts of a curing agent A to react to obtain a curing agent B; uniformly mixing 4 parts of the curing agent B, 7-8 parts of m-nitrobenzoic acid and 0.01-0.03 part of a catalyst to react to obtain a curing agent C; uniformly mixing 4-5 parts of the curing agent C and 5-6 parts of epoxy resin to react for 2-3h and adding 10-15 parts of water to obtain a curing agent D; uniformly stirring 2 parts of the curing agent D and 3-4 parts of epoxy resin to obtain a premixture E; uniformly mixing 150-200 parts of cement and 500-600 parts of quartz sand to obtain a premixture F; and uniformly stirring 1-2 parts of the premixture E and 5-20 parts of the premixture F and adding 1-2 parts of water to obtain the epoxy mortar. The preparation method provided by the invention has the advantages of prolonging the reaction time of emulsifying the epoxy resin by the curing agents, prolonging the working life and prolonging the service time of the epoxy resin, and construction is more convenient.