Huaying mountain,a karst mountain area,is located in the east part of Sichuan Province.The study area is about 1,500km~2,with its middle part bestriding the east and west wings of Huaying mountain anticline which presents a north-east trending silver shape.Over the anticlinal wings,karst strata and nonkarst strata alternately distribute.Bounded by non-karst strata constituting the aquitard,groundwater in the area mainly occurs in strip-shaped carbonate rock formations.Restricted by the conditions of stratum exposure,the karst water migrates in the direction from the southwest to the northeast.Since the 1980s,groundwater resources in middle regions of Huaying mountain area have drastically declined.The loss of the karst water has heavily affected both water supply to the local communities and development of regional economy.This paper discusses the factors and the quantity of water resources loss in the area.Through integrating analytical results of field survey and desktop study,the factors that have impacted on the water resources reduction,including climate change,social economic growth and human engineering activity,were identified.Among them the decrease of rainfall and the steep topography in mountain region have resulted in the shrink of water replenishment.In addition,social economic growth and expansion of human engineering activities both have led to great water consumption.According to the division method of karst water system,the groundwater units for water resources assessment in the study area were divided.On this basis,the water balance method was used to calculate the amount of water resources loss each year which is about 91.44*10~6 m~3.The volume of water loss in west wing of Huaying mountain is larger than that of the east wing.Moreover,the north part of the west wing has suffered from the most serious water loss in the area.By discussing the relationship between social,economic,environmental and water resources loss,this paper provides a certain basis for the comprehensive assessment and sustainable development of water resources in the study area.