The invention discloses an extension structure with expandable space. The extension structure comprises a vehicle body, four horizontal rods, two top plates, two bottom plates and two extension side walls, wherein the lower end face of the vehicle body is provided with a plurality of hydraulic support legs; the lower side of each opening is provided with two horizontal rods; the four horizontal rods are of telescopic structures, and are folded on the two sides of the vehicle body; each extension side wall comprises a first side wall plate, a second side wall plate and a third side wall plate; the two side edges of each first side wall plate are hinged to one side edge of the corresponding second side wall plate and one side edge of the corresponding third side wall plate; the other side edge of the corresponding second side wall plate and the other side edge of the corresponding third side wall plate are hinged to the two sides of the corresponding opening respectively. By adopting the extension structure with the expandable space, the practical use space can be expanded effectively, and the demands on the functions of folding and expanding the use space are met fully, namely, extra space is not occupied in a folding state; after being positioned, mounted and expanded, the extension structure can meet a relatively high residential functional requirement, and can be used repeatedly.