Abstract: To clear off the residual lubricant grease inside the welded steel tube left by the expanding process, the steel tube flushing system is used as a necessary equipment for the production line of welded pipes as used for the West-to-East Gas Transmission Pipe Line Project. Described in the paper are the design of the cantilever, a key component of the internal flushing unit of the said flushing system, and the anti-deformation manufacturing process of the cantilever which ensures the bending deformation of the cantilever to be minimized.