According to the special construction conditions of mountain area, the construction technology of the main beam erection of suspension bridge by rail cable slip method is put forward. In this method, the main cable and sling of the suspension bridge are used as the load-bearing structure, the lower end of the sling is connected with the sling saddle, the sling is supported on the rail cable, and the section beam is transported by the beam carriage moving on the rail cable. After reaching the installation position, the cable load crane is used for vertical hoisting and installation. Based on the construction of Aizhai super-large suspension bridge, the paper introduces the composition and key technology of the beam erection system with rail cable slip method, and the structural design and calculation analysis of the core components, such as the saddle, beam carriage and rail cable system. The test methods and results of the whole scale model test and full scale model test for the whole beam frame system are introduced, and the practical engineering application is summarized. The results of model test and engineering application show that the rail cable sliding frame beam method can quickly realize the erection of the main beam of the suspension bridge, and has good safety and economy, and has a broad application prospect.