The invention discloses a preparation method of 2-methoxy-4-nitroaniline. The preparation method comprises the following steps of: carrying out acetylation reaction of o-methoxyaniline and acetic acid, discharging water generated in the acetylation reaction process from a reaction system, dropwisely adding fuming nitric acid into the prepared acetic acid solution of the o-methoxyacetanilide to carry out nitration reaction, adding deionized water after the nitration reaction is finished and then filtering, adding the prepared 2-methoxy-4-nitroaniline into an alkali solution to carry out hydrolysis reaction; after the hydrolysis reaction is finished, cooling the prepared reaction solution, and filtering to obtain 2-methoxy-4-nitroaniline. By adopting the method to synthesize 2-methoxy-4-nitroaniline, the acylation reaction cost is low, the nitration reaction selectivity is high, the discharge of three wastes is reduced, the production cost is reduced, the product purity is high, the yield is high, and the 2-methoxy-4-nitroaniline has a good industrial application value.