Mesenchymal stem cells (MSCs) are capable of self-renew and multipotent differatiation which allows them to be sensitive to microenvironment is altered. Pulsed electromagnetic fields (PEMF) can affect cellular physiology of some types of cells. This study was undertaken to investigate the effects of PEMF on the growth and cell cycle arrest of MSCs expanded in vitro. To achieve this, cultured of normal rat MSCs, the treatment groups were respectively irradiated by 50?Hz PEMF at 10?mT of flux densities for 3 or 6?h. The effects of PEMF on cell proliferation, cell cycle arrest, and cell surface antigen phenotype were investigated. Our results showed that exposed MSCs had a significant proliferative capacity (P?0.05) at an earlier phase after PEMF treatment. Exposure to PEMF had a significant increase the percentage of MSCs in G1 phase compare with the control group, with a higher percentage of cells in G1 phase exposed for 6?h then that for 3?h. At the 16th hour after treatment, PEMF had no significant effect on cell proliferation and cell cycle (P>0.05). These results suggested that PEMF enhanced MSCs proliferation with time-independent and increased the percentage of cells at the G1 phase of the cell cycle in a time-dependent manner, and the effect of PEMF on the cell proliferation and cell cycle arrest of MSCs was temporal after PEMF treatment.