It is a structural component used to support PV modules, usually installed on the top of the PV bracket, and can connect the support structure and PV panels. It needs to have the characteristics of convenient installation, strong load-bearing capacity and corrosion resistance, and the main materials are aluminum alloy and steel. According to different cross-sectional shapes, it can be divided into Z-type, H-type and C-type PV purlins. Among them, C-type PV purlins have simple technological process and low production cost, and are mainstream products in the market.