Abstract: In this paper,the anomalous variation of water merecury befere 1998 Zhangbei M6.2 earthquake has been introduced.Its variation feature is shown by sharp variations in many points,big amplitude of the variation and long time period.At the same time,based on earthquakes examples with the water mercury precursor,the following features of the water mercury in Huailai No. 4 well have been concluded:many kinds of variation shapes,90-280 km distance from the well to the strong earth quake and 15-47 days time interval from the beginning of the anomalies to the occurrence of the strong earthquake.These would increase the knowledge on the relation of the water mercury precursor in this well with the strong earthquake and be advantage in the rise of the earthquake prediction with the water mercury.