Using the input-output analysis method,this paper sets up the input-output analysis mo-del of water resources,which reflects economic operation,water use and sewage discharge of national economic departments fully.Using the index of water input coefficient and total water input coefficient of industrial departments,this paper analyzes the characteristics of regional industry water utilization and taking the index of sewage discharge coefficient and total sewage discharge coefficient of industrial departments,the paper studies the effect of sewage discharge of regional industrial departments.Comprehensively analyzing the effect of water use and sewage discharge,the paper probes into the impact of industrial department products trade on regional water resources. Taking the city of Beijing as an example,the thesis has calculated the coefficients of water input and sewage discharge of every industrial department of Beijing in 1997.According to the result,we find,on the one hand,that some industrial departments such as agricultural and chemical,in which the coefficients of water use and sewage discharge were higher,the water use was inefficient,and the import volume of products trade in Beijing was relatively larger;on the other hand,the coefficients of water input and sewage discharge of other industries such as goods posting,electronics,service,etc,are much lower,their water use was more efficient,and their export volume of products trade was larger. Studies reveal that Beijing exported 1 499 420 000m³ of water with products trade,imported 3 040 010 000m³ of water,which resulted a net import of 1 540 590 000m³ of water;with products trade,Beijing exported 793 000 000m³ of sewage,imported 415 060 000m³ of sewage,which resulted in a sewage shift of 377 940 000m³.This indicated that Beijing's products trade in 1997 served as an effective means to alleviate the urgent water shortage situation. Finally,directed at more severe water resource situation in the future of Beijing,the thesis proposes that Beijing should consolidate and develop undertakings such as goods posting,elect-ronics,service industries,etc.,which belong to high efficient water use,trade and try to compress the industries in which water use is less efficient such as agriculture,food,electricity,textile,chem-istry,catering trade,papermaking,etc.,so as to mitigate water pressure by importing commodities promote water saving awareness,improve water use efficiency,establish water-saving industrial structure matching the characteristics of water resource of Beijing.