In order to accurately evaluate the reliability of the bridge under the alpine salt marsh area, the reliability evaluation index system was established by screening indicators from the aspects of the bridge's operational safety, service applicability, and material durability. The improved CRITIC-G1 method is used to determine the subjective and objective weights respectively, considering the influence of the indicators on the weights, and obtaining the comprehensive weights of the indicators according to the variable weight theory. It uses the set-pair-variable fuzzy set model for comprehensive evaluation, combined with the reliability evaluation characteristic value, and introduces the two-tuple linguistic method to conduct a second evaluation to further establish its reliability level status. Finally, an example is used to prove the effectiveness and operability of the model. It provides a theoretical basis for the later reinforcement and maintenance of concrete beam bridges in this area. And then provide suggestions for the prevention and reinforcement of small and medium-sized bridges in the area.