The aim of the present study is to investigate the effect of pulsed electromagnetic field (PEMF) on the activation of human monocytes (THP-1). Cultured THP-1 cells were exposed to PEMF stimulation with radiation of 32Hz or 64Hz respectively, using sinusoidal wave, and 1mT, twice a day, 30 minutes each time, with an interval of 8 hours, for 3 days. Those with 0Hz stimulation served as the controls. Monocytes activation was monitored by measuring both the release of monocyte chemoattractant protein-1 (MCP-1) from monocytes and their adhesion to monolayers of human umbilical vein endothelial cells (HUVECs). The adhesion of THP-1 cells to HUVECs was evaluated by cell counting method. The secretion of MCP-1 from THP-1 cells was detected by ELISA and MCP-1 mRNA expression was assessed by real time quantitative RT-PCR. The data showed that exposure to PEMF with above parameters could significantly inhibit the adhesion of THP-1 cells to HUVECs and decrease the MCP-1 mRNA and protein expression. The results demonstrated that exposure to PEMF of 1mT, 32Hz or 64Hz for 3 days could significantly inhibit the activation of THP-1 cells.