The main bridge of Lijiatuo Yangtze River double track bridge in Chongqing adopts the structural form of double tower and double cable plane cable-stayed bridge with asymmetric layout of track on the same floor, and its span is(68.4+150.8+454+161.3+102.2+50)m. The project is the key control bridge project of Chongqing rail transit line 18. It has the characteristics of wide disciplines, complex structure and various construction processes. In order to ensure the project quality, it is urgent to adopt forward design method. In order to ensure the high-quality and efficient establishment of BIM model and the effective transmission of model information between different softwares, the "R+GH+R" software system is adopted to carry out the whole process forward design. This paper describes the forward design analysis in the whole process of the design stage and the digital intelligence operation and maintenance in the process of construction and operation. With the help of the independently developed bridge scheme intelligent adaptation system, BIM model management system and digital intelligence operation and maintenance cloud platform, according to the customized secondary development, the technologies such as rapid generation of site model, interaction of computing information model, cloud computing, construction simulation, 720, VR and 3D printing are realized, the efficiency of scheme creation and positive design is greatly improved, and the product service chain of BIM technology is expanded. The forward design method is used to improve the design quality of bridge, and provide so as to provide reference for the application of BIM technology in the positive design of similar bridges.