Abstract: This paper investigates the bending performance of high-strength cold-formed C-shaped steel purlins in PV brackets. Span with six loading point concentrated loading tests are conducted on LQ550 high-strength cold-formed C-shaped steel purlins（hereinafter referred to as "C-shaped steel purlins"） under five different arrangements. Establish a finite element model for C-shaped steel purlins,and verify the accuracy of the model through test results of the bending performance of C-shaped steel purlins. Based on this model,explore the influence law of the relative slenderness ratio of purlins on their bending stability bearing capacity. According to the provisions of GB 50018—2002 "Technical code for cold-formed thin-wall steel structures",the beneficial effect of support rod constraints on the bending stability bearing capacity of purlins is analyzed. Based on actual projects,conduct on-site loading tests on PV brackets using C-shaped steel support rods. The research results show that:1) the bending stiffness and bending stability bearing capacity of purlins are significantly improved by setting support rod constraints between spans,and the improvement effect of setting C-shaped steel support rod constraints is stronger than that of circular tube support rods. 2) The C-shaped steel support rod can be regarded as an ideal lateral support,and the calculated length coefficient outside the purlin plane can be determined based on the setting of the C-shaped steel support rod. 3) The on-site loading test has proven that the C-shaped steel support rod has a good restraining effect on the torsion of the purlin,fully verifying the applicability of the new PV bracket structure using C-shaped steel support rod system.