Abstract: Based on the 1981-2009 dataset of the socio-economic and water environment of the Jiulong River Basin,an important region of the Western Taiwan Strait Economic Zone,the spatio-temporal relationship of river water quality with economic growth in the basin was analyzed,using statistical tools,GIS technique and environmnetal Kuznets curve(EKC)method.Compared with the rapidly growing secondary and tertiary industries,the slowly but steadily growing primary industry stood out in pollution creation.It increaed first and then decreased in cultivated area,and showed a linear rise in mean N and P fertilization intensity.Its N:P ratio(on a net nutrient basis)in fertilization declined from 4:1 in 1981 to 2:1 in 2009,which led to changes in nutrient stoichiometry of the river water,thus increasing the risk of algal bloom in the river.Marked differences existed between counties(cities or districts)in structure of pollution sources.The changes in water quality and the distribution of pollution along the river were closely related to the disposition of the socio-economy in space.The overgrowth of animal husbandry in the northern part of the Jiulong River Basin and the cash crop-based agricultural structure and the highly intensive,but low-in-use-efficiency fertilization in the western part of the Jiulong River Basin,were the causes triggering degradation(eutrophication)of the water quality since the 1990s.So far, the EKC curve has not yet shown any apparent turning point,indicating that water quality of the basin will go on degrading unless the pollution from agriculture is effectively controlled.