To investigate the characteristics of delayed rectifier potassium channel of cells under moderate intensity static magnetic field, the delayed rectifier potassium channel currents (IK) of acutely isolated mouse prefrontal cortex pyramidal neurons were examined. IK was measured and recorded after the neurons were exposed to 3 mT static magnetic field for 15,30, and 60 min. The results demonstrated that the 3 mT static magnetic field can change the characteristics of delayed rectifier potassium channel and reduce the amplitudes of IK. The maximum activated current densities of control group and 30 min exposure group were respectively 173.61 ± 30.68 pA/pF and 111.80 ± 17.17 pA/pF (n = 10, P <; 0.05). The half-activation voltage of the activation curves changed from -1.08 ± 2.17 mV to 10.63 ± 1.51 mV (n = 10, P <; 0.05) and the slope factor changed from 22.26 ± 2.99 mV to 17.90 ± 1.85 mV (n = 10, P <; 0.05). No change was noted in the inactivation process. The results show that moderate-intensity static magnetic field can change the characteristics of delayed rectifier potassium channel on the cell membrane, and further it may affect the physiological functions of neurons.