PTH building steel structure building is mainly composed of horizontal structure and vertical structure. Horizontal structure system is bent (including roof truss, beam and column) as the basic bearing structure, to bear the roof under load, horizontal wind load, earthquake action, the vertical load and horizontal level of crane load. Between the longitudinal structure system is made up of column, column support beams, walls, etc. In addition, there are houses, walls and roof support, to form a space rigid frame.