Abstract: Based on the observation data of water temperature at Luyang, Jingtai since 2011, we found the change and dynamic trend of water temperature of Luyang well has annual regularity. After eliminating interference factors of instrument failure, human disturbance and rainfall etc, we found some anomalies before the M_S4.7 Jingtai earthquake in Gansu. The method and the process of eliminating interference, and the application of the observed data after eliminating the interference can provide reference for tracking and analysis of the observation data.