Abstract: Cold-formed thin-walled steel structure is widely used because of its light weight, high strength, and easy construction. C-section member with web perforate is commonly used as a load-bearing member in cold-formed thin-walled steel structures. To investigate the influence of various buckling modes, i.e., local, distortional, global buckling and their interactions, on the behaviour of cold-formed steel beam-columns, a numerical study was undertaken to analyze the elasticity and elastoplasticity of cold-formed thin-walled C-section steel perforated member and investigate the influences of hole size, position and form on the member performance. Based on the numerical study, the direct strength method (DSM) curve for the compression member without holes was modified. The results show that the numerical model is verified by the existing test data. The holes will have a certain impact on the critical load of the member, and will reduce the bearing capacity. This study proposes the associated DSM design curve in cold-formed thin-walled C-section steel perforated member, and reveals the associated distortional and global buckling mode interactions.