The invention discloses a telescopic system used in a hoist, comprising a main girder, two pairs of telescopic girders, a pair of end girders and a telescopic chain device, wherein the main girder is formed by connecting a pair of cross girders and a pair of longitudinal girders; the top part and the bottom part of two ends at the inner side of each telescopic girder are respectively provided with a telescopic girder sliding plate, and the telescopic girders are arranged in a hollow cavity of the cross girders and slidably connected with the main girder; the end girders are arranged at two ends of the outer sides of the telescopic girders, and a hollow cavity is arranged inside the end girders; and the telescopic chain device is arranged in the main girder and further comprises a chain wheel driving device, a pair of pull rods and a pair of slide fasteners, wherein the chain wheel driving device is arranged in the cross girder of the main girder, sections of the pair of slide fasteners are respectively arranged on guide rails at the inner sides of the cross girders, the other sections are respectively arranged on the pull rods, one ends of the pair of pull rods are respectively connected with the end girders, and the other ends thereof are respectively connected with the chain wheel driving device. The telescopic system has simple structure and operation and favorable implementation effect.