Acutely isolated rats cortical neurons were exposed to 2450MHz radio frequency (RF) magnetic field, and the characteristics of delayed rectifier potassium channel were studied using the whole-cell patch-clamp technique. The 2450MHz RF magnetic field was obtained by Agilent E5070B net analyzer and a 6dB gain omni directional antenna, and the transmitting power was 39.81mW. The experiment revealed that the amplitude of delayed rectifier potassium channel current was reduced. The maximum activated current densities of control and 5min, 10min, and 25min exposure group were (191.71±29.82) pA/pF, (148.48±22.43)pA/pF, (120.95±17.29)pA/pF and (74.89±11.58)pA/pF respectively(n=10, P