Underground fluid monitoring is a common method for earthquake prediction. However, the correlations depending on statistic between the results of various underground fluids and earthquakes are usually not significant. In this study, based on a set of experimental instruments to monitor the hydrogen concentration escaping from the observation wells at Eryuan station, it was found that the hydrogen concentration changed dramatically before most earthquakes occurred in the surrounding area. Based on this finding, a detailed analysis of the changes in the hydrogen concentration in the wells is conducted to extract the changes that are related to earthquakes and to derive the related anomaly indicators. Then, the concept of the impact factor is proposed, and correlation analysis is performed with the impact factor and the integral value of hydrogen concentration at Eryuan. The results show that there is a significant correlation between the sudden changes of the hydrogen concentration at Eryuan and the neighboring earthquakes.