Abstract: A personalized QoS model is proposed for composition service to solve the problem that a single QoS model fails to consider fully such non-functional attributes in web service as subjectivity, relativity, dependency and uncertainty. The importance of criteria in view of the relativity of service is combined with the attention paid to service in view of subjectivity and uncertainty so as to form an initial weight vector. Then, the dependency is less considered to adjust the initial weight vector so as to get a personalized weight vector. As a result, the personalized QoS model is developed, on which the service functions are constrained and the dependency between criteria is less considered. The analysis of examples showed that the personalized QoS model thus developed is more reasonable and detailed than the single one through QoS evaluation.