Abstract: In this paper, the vertical Z component data of fluxgate magnetometer are used to calculate the corresponding relationship between earthquakes of M_L≥4.5 in Chongqing area （29.0°—32.0°N, 105.5°—110.8°E）. The results show that before the occurrence of earthquakes with magnitude M_L≥4.5, the anomalous phenomena of loading-unloading response ratio and daily variation amplitude ratio exceeding the threshold value occurs many times for at least two geomagnetic stations on the same day. It is considered that the comparison method with loading-unloading response ratio and daily variation amplitude can reflect the corresponding magnitudes in Chongqing and its adjacent areas better. The abnormal variation of threshold values of multiple sets of fluxgates in different models are also found in the same field.