p-Mononitrochlorobenzene is an important raw materials for synthesizing high energy materials. Its industrial production involving the concentrated mineral acids as the catalysts is one of the most environmentally harmful processes. Huge amounts of wastes along with a large amount of undesired o-mononitrochlorobenzene due to the nonselective nitration of chlorobenzene. Nitration of chlorobenzene by N₂O₅ was investigated with solid acid catalyst HZSM-5. For the excellent selectivity of HZSM-5,the ratio of p-mononitrochlorobenzene increased from 42% to 81%. Effects of reaction temperature,reaction time,amount of catalyst and the ratio of Si/Al on the nitration were investigated. When T=50 ℃,t=1 h and 5 g catalyst(Si/Al=260),the reaction condition is optimum,the yield of nitration of chlorobenzene was 50% and para-selectivity was 85.5%.