Abstract: The temperature and its gradient of 5 wells in Beijing area are measured and analyzed. The result shows that the effect of sun-radiation heat is regionally different and depends on the percentage of the sandy gravel particles and its size in the clay. The average water temperature gradient is different in different wells, the minimum value is 0.014℃/hm, the maximum is 3.376℃/hm. The difference is mainly related to hydrogeology structure, lithology of stratum and the tectonic condition. The micro-behavior characteristics of water temperature of well and the anomalies before an earthquake depend largely on the temperature gradient of the section in where the temperature sensor is fixed.