FPSO (Floating Production Storage and Offloading) plays a very key role in deep-sea oil and gas operations. Based on the construction project of a large FPSO topside modules, introduces the whole construction process of pipe rack module from prefabrication, assembly,weighing ad loading. Different from the conventional pipe rack module by pallets prefabrication, the whole construction effectively reduce the number of pallets, and the whole construction effectively saves all kinds of resources used in the prefabrication, spraying, lifting and other stage of pipe rack module, and solves the difficult problem of precision control in the conventional practice of H-shaped steel assembly group. At the same time, a support stool that can be reused in the assembly stage and weighing stage is designed, which saves a lot of machine tools and manpower input, further improves the economy and construction convenience of the construction of pipe rack module, provides a certain support role for the subsequent construction projects of the FPSO pipe rack modules, has greater engineering significance and value, and has obvious cost reduction and efficiency benefits. The application prospect is broad.