[en] Objective: To investigate the effect of 50-Hz, 1-mT pulsed electromagnetic field (PEMF) on the immunomodulation of human umbilical cord mesenchymal stem cells(MSCs) and to evaluate the safety of PEMF as a therapeutic strategy. Methods: Changes in cell viability was observed via MTT. Real-time PCR was used to detect the expression levels of cyclooxygenase 2(COX2), indoleamine 2, 3-dioxygenase(IDO), IL-10, hepatocyte growth factor(HGF), and transforming growth factor-β(TGF-β) in MSCs. To explore the safety of PEMF, a flow cytometry experiment was conducted to observe apoptosis and reactive oxygen species(ROS) level. DNA damage was detected via comet assay. Data were statistically analyzed via t-test with SPSS 19.0. P < 0.05 was considered statistically significant. Results: Cell viability increased, with the most obvious increase in 4 h/d(t = 3.505, P < 0.05). In interferon-γ(INF-γ)-activated MSC, the expression levels of immunomodulation factors improved after PEMF irradiation(t = 2.436 - 3.747, all P < 0.05). Furthermore, PEMF did not induce cell apoptosis, ROS generation, and DNA damage. Conclusion: 50-Hz, 1-mT PEMF improves MSC immunomodulation and may not cause radiation injury. (authors)