Background Prostate cancer is one of the most common urogenital tumors in the world with an increasing incidence in China. Androgen deprivation therapy is the major therapeutic option for advanced prostate cancer. However, the role of androgen receptor (AR) in hormone-refractory prostate cancer still remains unclear. This work aimed to investigate the role of AR in an androgen independent prostate cancer cell line by in vitro and in vivo studies.Methods The role of AR in the proliferation and invasion/metastasis ability of PC3-AR9 (a PC3 stable clone expressing human AR driven by natural human AR promoter) were examined with MTT assay, soft agar assay, chamber invasion assay, wound healing assay, and also with orthotopic xenograft mouse model.Results Restoring androgen receptor in PC3 cells resulted in decreased proliferation and invasion/metastasis ability in MTT, soft agar, chamber invasion and wound healing assay. In the mouse orthotopic xenograft model, PC3-AR9 resulted in smaller primary tumors and metastasis tumors, with a lower proliferation rate and higher apoptosis rate.Conclusion The AR might function as a tumor suppressor in PC3 cells both in vitro and in vivo.