The invention discloses a synthetic method of N-methyl-4-(methyl amino)-3-nitrobenzamide. The method comprises the following steps: firstly, 4-chloro-3-nitrobenzoic acid and methylamine react to generate 4-methyl amino-3-nitrobenzoic acid; then 4-methyl amino-3-nitrobenzoic acid and thionyl chloride have an acylating chlorination reaction to generate 4-(methyl amino)-3-nitrobenzoyl chloride; and finally, 4-(methyl amino)-3-nitrobenzoyl chloride and methylamine react to obtain the N-methyl-4-(methyl amino)-3-nitrobenzamide. The synthetic method of the N-methyl-4-(methyl amino)-3-nitrobenzamide has the advantages that raw material source is wide, the price and the production cost are low, the synthetic process is simple, the operation is simple and convenient, short time is consumed, the product yield is very high, and the total yield of the final product can reach 97.5%