2,6-dihydroxy-3,5-dinitrotoluene (MDNR) is one of key intermediate for poly(p-phenylene methyl benzobisoxazole) (MPBO) . In this paper, 2,6-dichloro-3,5-dinitrotoluene (DCDNT) was first prepared through the nitration of 2,6-dichlorotoluene with a purity of 99.79% and yield of 98.40%, then methoxylated with CH3O- to obtain 2,6-dimethoxy-3,5-dinitrotoluene (DMDNT) with a purity of 96.90%，and a yield of 88.36%; Finally, MDNR was successfully synthesized by the acid demethylation of DMDNT, and its purity was 99.40%，the yield was 93.15%. MDNR was identified by FT-IR, MS and 1H-NMR. This process has advantages of cheap raw materials, convenient operation, excellent product quality, the total yield of more than 80%, easy to industrialization,etc. which provides the source of key intermediate for further development of methyl modified PBO fiber.