Abstract: This paper uses the precursor observation data of the YRY-4 borehole strain gauge at Zhaotong seismic station to extract the interference events of rainfall on the observation data of the instrument. The results show that when the total rainfall reaches 40 mm and the instantaneous maximum rainfall is greater than 0.4 mm, the observation data of the YRY-4 borehole strain gauge is obviously disturbed by the rainfall; when the total rainfall is greater than 40 mm, the total rainfall and the observation data is a linear relationship between the strain variables. There is no significant corresponding relationship between the instantaneous maximum rainfall and the total rainfall. The analysis shows that the influence of rainfall interference mainly comes from rainfall infiltration and the load capacity of the geological water body around the station. Quantitative analysis of rainfall disturbance is helpful to distinguish the difference between anomalies and disturbances, and to accumulate experience so as to facilitate anomaly determination timely and effectively and serve earthquake research.