With the increase of traffic volume, the enlarging tunnel span and the decreasing of surrounding rock integrity, the level of surrounding rock will be lower. This article proposed the calculating method of relative integrity index based on the concept of relative integrity of surrounding rock and established the Fuzzy Comprehensive Evaluation Method for rock classification by analyzing the impact of tunnel span enlargement upon rock stability. It also specified the determination factors, discussed the selection of weight indexes and proposed methods of establishing the qualitative and quantitative subordinate degrees. Based on practices of the expressways of Fuzhou, Xiamen and Zhangzhou, this article made fuzzy comprehensive evaluation of rock classification and fully analyzed the results of the evaluation. Results showed that with the enlargement of tunnel span, levels of surrounding rock would lower accordingly, and that the worse surrounding rock was, the more it would lower.