China s construction project mean tender methods include reasonable low price bid evaluation, general grading method and tow-stage evaluation method etc.. These evaluation index systems were proved to be effective and feasible. However, some of them need to qualitative evaluation score; it is inevitably arbitrary and artificial factors. A mathematic model based on fussy mathematics and gray relational analysis was used to construct a comprehensive evaluation index system and to build a simple and effective practical model. Provided valuable theoretical basis for choose the successful bidder.