Selecting high quality web services based upon QoS(Quality of Service) is a significant task in service-oriented computing environments. In this paper, according a real Quality of Web Service data sets:QWS Dataset (1.0), we developed a Weighted Grey Relational Analysis Model(WGRAM) for web service selection based on QoS, and combined with Analytic Hierarchy Process(AHP) and Grey Relational Analysis (GRA) to prioritize the relative importance of the QoS of web services. The comprehensive evaluation model (WGRAM) fully considered the influence of many factors given by experts, incorporating the qualitative analysis of the index of various factors and the quantization for scientific decision-making, it can provide weighted grey relational degree for each Web Services with the same functions(operations), and the grey relational sequence which can guide the optimal service selection from multiple functions similar service. The model possessed the characteristic of simple calculating process, and the result was reliable, It’s a reliable and effective method of web service quality factor assessment and a significant attempt for web services selection.