The effects of static magnetic fields at 150 to 155 mT on the activities of superoxide dismutase (SOD) and the contents of maglonydiadehyde (MDA) in the serum and the activities of glutathione peroxidase (GSH-Px) in the whole blood were observed in the healthy volunteers. The results showed that the activities of SOD and GSH-Px were significantly increased, and the content of MDA was significantly decreased in short term at the observed magnitude of static magnetic fields. The results suggest that the function of the free radical metabolism of human body could be improved by static magnetic fields at that magnitude.