Abstract: In order to evaluate the accuracy of daily variation records of geomagnetic field by relative record instruments correctly,we analyze the baseline value accuracy and stability of 2 sets GM4 type fluxgate magnetometer in Hongshan standard seismic station using geomagnetic records from 2009 to 2012, meanwhile study the correlation between the baseline value changes and geomagnetic daily records.Then we get the following conclusions:during the calibration, the D, H, Z three component of two sets GM4 type fluxgate magnetometer baseline value change and measurement error are both very small; the No.1 GM4 type fluxgate magnetometerruns more stable than the No.2 GM4 type fluxgate magnetometer, and its diurnal variation record accuracy calibration baseline relationship is not significant relationship between the value and the daily variation of geomagnetic field, which maybe related to the aging of the two sets instruments and the observation environment factors; during 10:30 to 12:30 and after 15:30, the daily variation of geomagnetic field recording accuracy calibration baseline value is morestability, so it is suitable for the geomagnetic absolute observation in this time period.