Abstract: All that briefed here in the paper are issues concerning square steel tubes,including the mechanical properties of large-sized square steel tube and round steel tube when serving for steel structural beams (columns),market survey of square steel tube and technical level of manufacturing equipment therefore,etc.It is finally concluded that the current increasingly expanded domestic production capacity of square steel tubes has been bigger than actual market demand,and therefore the development philosophy in this field needs to be transformed from the quantity expansion type into the quality and innovative expansion.