Masonry lining is very important in railway line, and it is influenced by many factors in operating pro- cess. Lining diseases may often have negative effects on running safety. Based on masonry lining disease infor- mation of Chengdu Bureau, by analyzing the distribution of masonry lining diseases, this paper established ma- sonry lining tunnel safety evaluation system according to AHP, introduced relative difference function to identify indicators for each membership level of security and obtained the value of the safety evaluation masonry lining of the tunnel through a variable recognition model. The evaluation of typical tunnel shows that using relative differ- ence function masonry lining tunnel safety evaluation is feasible, and the evaluation results are more reasonable, which can provide the basis for the maintenance of masonry lining of the tunnel.