The research on evaluation method of manufacturing enteraprise informatization(MEI) is the core of informatization evaluation system. According to the characters of MEI, a gray clustering evaluation method on combinative weight-fixing is brought forward . In the way to fix the index weights, firstly the advantages and disadvantages of the subjective and objective weight-fixing method are analyzed compositively. Then the subjective weights are gained from Analytical Hierchy Process(AHP) method and the objective weights from Gray Relating Analyses(GRA) method. Last the final indexs’ weights are gained from the combinative weight-fixing method based on the minimum error of optimizing project, which takes in the full advantages of the two methodes. Finally the informatization construction process is devided into certain Gray Types, and the informatization benefits are calculated with Gray Clustering method based on Whiten Function. In the end Three enterprises are chosen to analyze with gray clustering evaluation method on combinative weight-fixing.