To explore the expressional information of PIWIL4 in human ovarian cancer, semi-quantitative reverse transcription polymerase chain reaction (semi-qRT-PCR) was used to detect the mRNA expression level of PIWIL1, PIWIL2, PIWIL3 and PIWIL4 in human ovarian clear cell carcinoma ES-2 cells. Meanwhile, in human ovarian cancer and adjacent normal tissues, the mRNA expression of PIWIL4 was determined. Then, PIWIL4-siRNA, which was designed to target PIWIL4 and chemical synthesized, was transfected into ES-2 cells with lipofectamine. MTT assay and clone formation assay were used to investigate the effects of PIWIL4-siRNA on the cell growth activity and proliferation capacity of ES-2 cells. Experimental results showed that the mRNA expression level of PIWIL4 was the highest compared to PIWIL1, PIWIL2 and PIWIL3 in ES-2 cells (P < 0.05), and the expression of PIWIL4 mRNA in ovarian cancer tissues was higher than that in adjacent normal tissues (P < 0.01). MTT and clone formation analyses demonstrated that the cell growth activity and clone formation ratio of PIWIL4-siRNA transfected ES-2 cells were markedly decreased (P < 0.05). In conclusion, the expression of PIWIL4 mRNA was highest in ovarian cancer cell line ES-2 cells and was significantly increased in ovarian cancer tissues. Moreover, PIWIL4-siRNA can efficiently inhibit the cell activity and proliferation ability of ES-2 cells. In a word, PIWIL4 may be related to the pathogenesis of human ovarian cancer.