20(S)-9-nitrocamptothecin was synthesized from camptothecin by nitration reaction using mixed nitrate salts in sulfuric acid medium.The yield was raised from 31% to 40% after chromatographic purification treatment.The best reaction conditions was as follows:0.5 g of camptothecin;30ml of sulfuric acid;0.007mol of nitrate salts(NH4NO3/CaNO3=1/1).The reaction was completed in 24h at 20℃.The advantage of this method is high yield and easily purification.