Grassland eco-system service provides a natural environment condition and function that grassland eco-system forms and sustains human being survival.And it does not only offer raw materials for husbandry,but also some regulating and supporting services.In fact the latter function and their values are most important,but usually neglected.In recent 20 years,excessive grazing has exerted severe negative influence on grassland eco-system services,especially on its environment sustaining service,and the resultant economic losses are very great. Thus this paper discusses the effects of excessive grazing on grassland eco-system services values,by taking Maqu county as an example and analyzes its grassland conditions by taking grassland conditions in the 1980s as pre-excessive grazing and the present conditions as post-excessive grazing.Firstly,based on the analyses of grassland eco-system,the index system of effects of excessive grazing on grassland eco-system services valuation was constructed,includingood production,atmospheric regulation,nutrition circulation and storage,erosion control,water conservation and environmental purification.Then by choosing reasonable ecological economic methods and parameters based on other's researches,assessment method of every index was established.Finally,using the above methods,the economic losses of excessive grazing were primarily estimated. The results showed that economic losses in food production,atmospheric regulation,nutrition circulation and environmental purification values of grassland in Maqu county in the 1980s were 4.28×108 yuan,2.96×109 yuan,2.84×108 yuan and 8.3×107 yuan,respectively,while at present those values were 2.78×108 yuan,1.92×109 yuan,1.85×108 yuan and 5.4×107 yuan,respectively.Due to excessive grazing,the economic losses of food production,atmospheric regulation,nutrition circu-lation and storage,erosion control,water conservation and environmental purification services were 1.50×108 yuan,1.04×109 yuan,0.99×108 yuan,1.02×107 yuan,3.94×108 yuan and 2.9×107 yuan,respectively.The total economic losses reached 1.72×109 yuan,in which direct economic losses accounted for 8.7%,and indirect economic losses were enormous and accounted for 91.3%.Among these services,the values of atmospheric regulation and water conservation services were higher,while those of erosion control and environmental purification services were lower.