Structural instability of polymers under strong acidic condition severely limits their application in the field of environment. A synthetic strategy for the preparation of poly(m-phenylenediamine)/reduced graphene oxide (PmPD/rGO) composites was proposed for Cr(VI) removal in strong acidic solution, which involved in situ reduction of graphene oxide (GO) and assembly of PmPD nanoparticles. Effects of in situ reduction of GO on oxidation polymerization, property and Cr(VI) adsorption capacity of composites were investigated methodically. Compared to pure PmPD, PmPD/rGO composites exhibited favorable stability in strong acidic solution. Moreover, the polymerization yield of PmPD/rGO composites increased from 75 to 91%. The maximum Cr(VI) adsorption capacity of composites calculated by the Langmuir model reached 526.24mgg(-1). The mechanisms of PmPD/rGO composites preparation and Cr(VI) removal were analyzed in detail. The synthetic strategy shows promising prospect to expand application of polymers, especially for Cr(VI) removal in strong acidic solution.