The invention discloses a rectangular tube truss without a support. A truss body is provided. The truss body comprises four main chord rods and a plurality of diagonal rods and vertical rods which are fixedly connected with the main chord rods, wherein crosspieces are arranged between the vertical rods; end parts of the crosspieces are fixedly connected with the vertical rods; the main chord rods, the diagonal rods and the vertical rods are all arranged into tubular structures with rectangular cross sections; the crosspieces are made of box iron or angle steel; a connection plate is fixedly connected to two sides, close to the crosspieces, of the vertical rods respectively; each connection plate is fixedly connected with two end parts of the crosspiece through bolts; and the main chord rods are tightly fixed at the upper end parts and the lower end parts of the vertical rods through bolts and fixedly connected with the diagonal rods through bolts. According to the large-hoisting-height rectangular tube truss without a support, the stability of the truss is increased; the hoisting height can be allowed to be the maximum height of 14 m; and for certain occasions when middle supports cannot be used and a large hoisting height of an escalator is required, the rectangular tube truss can meet the requirement.