The catalysis of O/W microemulsions of cetyltrimethylammonium bromide(CTAB), butyl alcohol, benzene and water to the hydrolysis of 2,4-dinitrochlorobenzene(DNCB) was studied. Hydrolysis of DNCB in microemulsions under normal temperature and normal pressure was realized. The results showed that the rate constants of hydrolysis of DNCB decreased with the increase of benzene content anti the ratio of cosurfactant to CTAB. As cosurfactant, t-butylalcohol is bet.ter than n-butyl alcohol for the reaction.