M-nitrobenzyl bromide and 1-(dibromomethyl)-3-nitrobenzene, which were prepared with m-nitrotoluene, hydrogen peroxide and hydrobromic acid over AIBN, was oxided and hydrolyzed to produce m-nitrobenzaldehyde. Factors influencing bromination, hydrolysis and oxidization were studied. Under the optimal bromination conditions: bromonation temperature 60 ℃, bromination time 4 h, n(m-nitrotoluene) : n(HBr) : n(H2O2) 1:2.5:2.5, the amount of AIBN 0.8 g. Under the optimal oxidization and hydrolysis conditions: oxidization temperature 105 ℃, heat preservation time 8 h, hydrolysis temperature 60 ℃, hydrolysis time 1 h. The yield of m-nitrobenzaldehyde is 58.6%. Purity of product reaches 99.1%. The structure of the product was identified by IR and 1HNMR.