It is inevitable for railway construction to avoid crossing a series of large water area, so sometimes large span railway bridges must be considered. There are various differences between the high-speed railway bridges and the ordinary railway bridges, such as the stiffness, durability, integrity, smoothness, dynamic effect and maintenance. So there are also some differences in the design methods. The design and construction of the over-channel railway lines is becoming imperative with the rapid progress of China's railway engineering. By choosing railway suspension bridge design as the engineering background, a steel truss suspension bridge with the span of (200+600+200) m is analyzed. Steel truss with superior performance such as good ventilation and torsional mechanics can be advantages and widely used in long-span bridge. The process of the design is as follows: Firstly, through accessing relevant norms, determine the size of the structure in this paper. Secondly, the FE model of the bridge structure is built by using the software of MIDAS to calculate the internal force. According to the determined forces, check the stress calculation in the part of the rod cross-section for a certain change. Finally, according to relevant regulations, check the main cable, sling, pylon, stiffening girder joints.