The invention provides a connecting structure of an aluminum square tube unit. The connecting structure comprises an aluminum wood-grain-like square tube, a top installation base layer and a bottom installation base layer and also comprises a first positioning component and a second positioning component, wherein the first positioning component is fixed on the top installation base layer; the second positioning component is fixed on the bottom installation base layer; the first positioning component is inserted into an upper port of the aluminum wood-grain-like square tube; the second positioning component is inserted into a lower port of the aluminum wood-grain-like square tube; and motion of the aluminum wood-grain-like square tube in the horizontal direction is limited by the first positioning component or the second positioning component or both the positioning components. The connecting structure of the aluminum square tube unit disclosed by the invention has the beneficial effects that a finished product is installed on site; welding and rust-proof processing are not needed; open fire operations on a construction site are reduced; a part of hidden safety hazards can be eliminated; and operations of professionals are not needed.