Abstract: The earthquake records from Jan.of 2002 to Jun.of 2003 recorded by each station in the digital telemetered seismic network of Capital Area are processed.The data in 58 stations that its sample number is over 100 are sorted, and the deviation, mean deviation and standard departure for magnitude in each single station are calculated.The cause of deviation is analyzed and the correction for each station is presented.The sample number that its deviation is within 0.2 reached 70% after correction.The results show that the gage function tends to smaller when the epicentral distance is within 0~40km.The deviation of magnitude comes mainly from the synthetical affection of each station.