Based on the land use/cover data of 1995 and 2004, and by using ecosystem service value per unit area of different terrestrial ecosystem types in China, the dynamic changes of ecosystem service value in Pinggu District of Beijing were analyzed. The results showed that the total ecosystem service value of Pinggu District was decreased from 3.291 x 10(9) yuan in 1995 to 3.044 x 10(9) yuan in 2004, with a change rate of -7.50%. The decrease in the areas of farmland and waters was the primary cause of the loss in ecosystem service function. Aquatic ecosystem had the highest ecological service value per unit area, while forest ecosystem gave the greatest contribution to the total ecosystem service value. The dynamic changes of the ecological service value revealed the conspicuously irrationality of land use structure in the District. The area proportions of forestland, farmland, and waters should be increased, and the conversion from farmland to constructive land should be controlled strictly. As the emergency water source and eco-conservation division of Beijing City, Pinggu District should improve its eco-environment protection and economic development to support the ecological and drinking water source securities of the Capital Beijing.