Objective：To investigate the effects of dihydroartemisinin（DHA） on regulating ubiquitin carboxyl-terminal hydrolase L1（UCHL1） gene expression in human prostate cancer cell line PC-3 and its mechanism. Methods：PC-3 cells were divided into six groups including four groups treated with DHA at concentrations of 12.5，25，50，100 μmol/L；5-Aza-CdR group cultured in the media with 5-Aza-2’-deoxycytidine at concentrations of 2.5 μmol/L and blank group cultured with blank media. CpG island of ubiqui－tin carboxyl-terminal hydrolase L1（UCHL1） methylation levels were determined by bisulfite genomic sequencing. UCHL1 mRNA expression levels were determined via realtime fluorescence quantitative PCR whereas the expression levels of UCHL1 protein were determined using Western blot. Results：In the DHA groups and 5-Aza-CdR group，UCHL1 promoter methylation levels were decreased dramatically（χ2=150.1，P=0.000； χ2=127.7，P=0.000）. mRNA expression levels of UCHL1 were dramatically increased（ χ2=150.1，P=0.000； χ2=127.7，P=0.000）. Protein expression levels of UCHL1 were significantly increased（P<0.05）. In DHA groups，mRNA ex－pression levels of DNA methyltransferase were decreased（P<0.05）. Conclusion：DHA can induce the demethylation of CpG island of UCHL1 through downregulating the expression of DNA methyltransferase in PC-3 cells.