In order to collaboratively and optimally control the key elements of the technical interface of the railway bridge-tunnel in the arduous mountainous area, the tradeoff optimization model of the key elements for the technical interface was established, which was combined the multi-attribute utility function and the "three-one" elements transformation structure. Firstly, the relationships among quality, schedule, cost and safety were analyzed and quantified by functional forms. The "three-one" elements transformation structure was employed to determine the "main attachment" dimensions, and the tradeoff optimization function of the key elements for the technical interface of the railway bridge-tunnel in the arduous mountainous area was established. Then based on the mechanism that the technical interface to the key elements, the decision preference coefficients of the tradeoff optimization function were determined by ANP, the achievement scalarizing functions preference inspired co-evolutionary algorithm (ASF-PICEA-g) was used to obtain the optimal solution of the tradeoff optimization model, and find the optimal solution of each key element under the optimal solution of the whole model. Finally, both the rationality of the tradeoff optimization function and the effectiveness of the ASF-PICEA-g were verified by constructing the tradeoff optimization function of the technical interface between the Zangmu Bridge and the Allah Tunnel and carrying out the optimization analysis.