Glucose-regulated protein 78 (GRP78) plays an essential role in embryonic development and in the progression and therapeutic resistance of many cancers. However, little is known about the function of GRP78 in hormone-independent prostate cancer. Here, we found that the expression levels of GRP78 were higher in PC-3 cells than in DU-145 cells. When the expression of GRP78 was silenced using a GRP78-specific small interfering RNA in PC-3 cells, the growth rate and adhesive ability were reduced. Cell migration was dramatically decreased in GRP78-depleted cells. Dissection of the involved signal pathways revealed that maspin expression was upregulated after silencing GRP78 expression. The upregulation of maspin and downregulation of COX-2 may cause the decrease in cell proliferation and migration observed after silencing GRP78 expression. Silencing GRP78 expression may suppress the proliferation, adhesion, and migration of prostate cancer cells via maspin and COX-2 regulation.