The steel truss system is divided into triangle truss, trapezoid truss, parallel chord truss and polygon truss. Its main structural feature is that the stress of each member is mainly one-way tension and compression. Through the reasonable arrangement of upper and lower chords and web members, it can adapt to the distribution of bending moment and shear force inside the structure. Due to the horizontal tension and compression internal forces to achieve their own balance, the whole structure does not produce horizontal thrust bearing. The structure layout is flexible and the application range is very wide. Truss structure is often used in large-span factory buildings, exhibition halls, gymnasiums, bridges and other public buildings.