Abstract: There are multiple factors affecting the optimal selection of the high speed railway route.The factors are interactive.To obtain the optimized route scheme,the set pair analysis method is used.From the perspective of geologic factors,the analysis and evaluation on geological factors affecting the rail lines are made.For choosing the best route line,the analytic hierarchy process(AHP)is used to determine the rate of the various influencing factors.The set pair analysis(SPA)is used in variable fuzzy sets calculation.In this paper,the principles and steps of the AHP and SPA are described and analyzed.Then,this paper takes the six schemes in Daba Mountains of the high-speed railway program,a segment of the Xi'an to Chengdu railway,for the research objects.The investigation includes the study data collection of the engineering geological conditions,field investigation,the indoor data analysis.The paper determines six evaluation factors which have the impact on the selection of the proposed lines.Through a nine-scale method,the matrix of the evaluation factors on the rail program is obtained.From AHP calculation,the rates of evaluation factors are obtained.The SPA is used for the pros and cons evaluation of each line and to select the best alignment of optimal design.It is concluded that among the suggested six lines,the DK1 is the best one.