Due to the limitations of assessment on the state of long-span bridges based on of the existing highway bridge evaluation standards, the comprehensive evaluation method of cable-stayed bridges was conducted. On the basis of the current standards for technical condition evaluation of highway bridges, a new comprehensive evaluation index system was established by introducing of some special components and long-term monitoring data. Considering the traditional weighted calculation method is easy to cover the situations of the big differences among of the indexes, a comprehensive assessment model with multi-index evidences fusion was proposed based on the credibility. In this model, a piecewise linear criterion of the evaluation index was used in underlying layer firstly. The basic confidence was determined by the membership and weight, and the fuzzy membership was calculated by the ridge type distribution function. Secondly, the confidence of the upper layer was composed by an improved Dempster combination rule. A large span cable-stayed bridge in Jiangsu Province was taken as an example, and the standard method and the improved method were analyzed based on the periodic inspection reports during 10 years. The results show that the conclusions using the advanced method agree well with the actual defects and maintenance conditions. The evaluation category is more reasonable, and the confidence set could present the state of the structure more comprehensively compared to a single value.