Abstract: Objective To study the effects of dihydroartemisinin (DHA) on inducing apoptosis of human prostate cancer PC-3 cells and investigatesthemorphological changes. Methods Prostate cancer PC-3 cells were transplanted into 20 nude mice to establish the solid tumor mode. These nude mice were randomly divided into 4 groups with 5 mice in each group: control group, solvent group, low dose DHA group and large dose DHA group. The tumor growth inhibition rates were calculated on day 13 after drug administration. Pathomorphism changes of PC-3 cells were observed by light microscope (LM) after administration of DHA. Apoptosis cells were detected by HE staining,TUNEL method and Hoechst 33258 fluorescence staining. Results The tumor growth inhibition rates of large dose DHA group and low dose DHA group were 69.221% and63.186%, respectively.LM revealed that the scatteredapoptotic cells were observed in tumor tissues of DHA groups. TUNEL stainingevealed that the rate of cell apoptosis raisedsignificantly(P＜0.05). Fluorescence microscope examinationindicatedthat the apoptotic cells stained by Hoechst 33258 significantly increased in tumor tissues of DHA groups. Thedensity of apoptotic cell significantly augmented (P＜0.05). Conclusion These results demonstrated that DHA had stronger inhibitory effects on human prostate cancer cell line PC-3 cells in vivo.The action mechanism might be related toDHA inducing the apoptosis of prostate cancer PC-3 cell．