A key problem of the Web service is how to evaluate the reputation of the Web service. When the multiple attributive decision-making problem bases on the incomplete attribute weight and determinate attribute value, a new grey relation analysis method is proposed to solve the problem of evaluating the reputation about semantic Web service. According to the fundamental principle of the grey relation analysis method, this method gives the calculating procedure to solve the problem of evaluating the reputation when the attribute weight of semantic Web service is incomplete. The core of the method is building and solving a single-purpose linear programming model and an optimum model of optimal membership degree. An instance is described in the paper to illustrate that the grey relation analysis method is a good method to resolve the problem of evaluating reputation when a semantic Web service has incomplete attribute weight. the simulation results of experiment shows that, compared with the traditional evaluating method which use blurring operators, the new method increases precision ratio and recall ratio of web services.