1.Shaanxi Coal North Mining Co.， Ltd.， Yulin ， China； 2.Hanjiawan Coal Mining Company Ltd.，Shaanxi Coal North Mining Co.， Ltd.，Yulin ，China；3.Institute of Land Reclamation and Ecological Restoration， China University of Mining and Technology-Beijing，Beijing ， China；4.College of Civil Engineering， Henan University of Engineering， Zhengzhou ，China

In view of the damage of land ecological environment due to coal mining in the ecological-fragile coal mining areas in western China， a mine in the ecological-fragile mining area of northern shaanxi was taken as the research area， TDR field measurement and statistical analysis were used， based on previous research results，the relationship between dynamic ground crack due to coal mining development rules and changes in soil water content in the mining process was studied and analysed.The results indicate that the variation of surface soil water content above the goaf is consistent with the dynamic development rules of dynamic ground cracks，soil water content around the crack gradually decreased when the crack emerged and extended； There is a corresponding slight rebound when the crack first closed；and the soil water content decreased when the crack extended again； With the working face advances， soil water content increases with the closure of the existing cracks.There is some influence extent of dynamic crack on the soil water content， the influence range is ea 70 cm，in other words， the soil water content changes obviously when approaching the ground crack， the soil water content basically remained unchanged when the distance from the monitoring point to the crack exceeded ea 70 cm，and there is a influence cycle of ground crack on soil water content， the influence cycle is consistent with the development cycle of the dynamic ground crack， the changes of soil water content is closely related to the development cycle of ground cracks，the cracking and close of ground cracks have certain impact on the soil microstructure， then affecting the evaporation and permeation of soil water， the soil water content could restore to the pre-mining level at last after the cracks close.This study is characterized by small research scale in one selected working face，which is helpful to the study on the influence mechanism of coal mining on land ecology in ecological-fragile mining areas.