The invention relates to a novel two-dimensional single-side expansion nozzle and belongs to the technical field of aero-engine nozzles. The nozzle comprises a round-to-square barrel (1), a single-side expansion wall (3), an adjustment plate (4), extension section side walls (5) and a shield swirling leaf-shaped structure (6) and is particularly characterized in that the front end of the round-to-square barrel (1) is connected with an engine and serves as a support member of the whole nozzle; the rear end of the round-to-square barrel (1) is connected with the single-side expansion wall (3), the adjustment plate (4) and the extension section side walls (5); and the shield swirling leaf-shaped structure (6) is fixedly mounted in the round-to-square barrel (1) and mainly used for shielding a hot end member at the front end of the nozzle to achieve a good invisibility function. The nozzle has the advantages that a structure size of the conventional two-dimensional single-side expansion nozzle is ensured, a defect of the poor invisibility function of the conventional two-dimensional single-side expansion nozzle is overcome, and the nozzle has the advantages of simple structure and high reliability at the same time.