Based on the data of environment，society，economy，and water resources of Tarim River basin in 2005，we evaluated the water resource carrying capacity of the basin using a variable fuzzy model． The results show that the method identified reasonably the relative degree of membership and relative membership function of the individual index in each index group，and it also determined properly the classes that each sample belongs to by changing the model with its parameters，greatly improving the reliability of the assessment． The water resources carrying capacity of Tarim River basin belongs to the second class，showing a high degree of water resource utilization level． It is important to improve the water carrying capacity by adopting some fundamental measures，which include converting the economic structure from water over-consuming to water saving，balancing water uses among the areas of the upper and lower reaches，carrying out integrated schemes of water exploitation and utilization，and developing a decision-making supporting system covering the whole Tarim River basin．