Novel BrØnsted ionic liquid 1-metyl-3-propanesulfonic acid immidazolium hydrogen sulfate［MIMPS］［HSO₄］ was prepared as catalyst for the green chemical processes of nitration reaction. Nitration reaction was carried out for 10 h at 60 ℃ with the catalyst to reactant molar ratio of 1∶50, and the yield of mononitration reaction was 70.4%, and selectivity of mononitration reaction was 100% with a para to ortho ratio of 0.7. Biphasic system of product and catalyst was obtained and the product could be separated simply by decantation. In addition, ionic liquid could be recovered and reused showing the possibility of a clean chemical process.