The invention belongs to the technical field of chemical synthesis of medicaments, and discloses N-substituted benzene ring 3,5-pyrazodione compounds with antitumor activity, a synthesis method and application thereof. The compounds have a structure shown in a general formula I, wherein in the formula, R1 is hydrogen, m-methyl, p-methyl, p-chlorine, and p-bromine; R2 is p-benzyloxy, p-hydroxy, p-chlorine, and p-bromine; R3 is n-butyl, isobutyl, cyclopropyl methyl, and benzyl; and R4 is hydrogen or hydroxy. The compounds are used for treating tumor diseases; and in vitro anticancer activity experiments prove that the compounds have obvious inhibition and killing effects on a plurality of tumor cells, and can be taken as active components to be applied to clinical prevention and treatment of cancer after the compounds are developed into novel medicaments.