The utility model discloses a small-size tire dismounting and mounting machine with a tire expanding mechanism. The tire expanding mechanism takes a swing frame as a framework; and a roller is fixed on the tire expanding mechanism by a screw through an angle iron frame hole. A tire expanding hook and a locking cam form an integrated part; a swing frame locker and a power supply and air source box are respectively fixed on the swing frame through screws; a reversing valve is fixed on the side of the swing frame through screws; an air cylinder rear end cover and the end part of a piston rod are respectively hinged to a support rib of the swing frame and a tire expanding support arm; a middle hole of the tire expanding support arm is hinged on the swing frame; and a support arm tire expanding hook is hinged to an upper end hole of the tire expanding arm. A work lamp, a patching tool box and a tool hanging piece are respectively fixed on a support lug plate at the upper part of an upright post of the disassembly and assembly machine, at the upper part of the upright post and under the upper patching tool box through the screws; in the tire expanding mechanism, a rotating shaft sequentially penetrates into shaft holes of an upper mounting base, a swing frame and a lower mounting base; and the upper mounting base and the lower mounting base are respectively fixed on the upright post and a box body of the disassembly and assembly machine. The small-size tire disassembly and assembly machine has the advantages of compact structure, two functions of two sets of mechanisms in one machine, resource and material economization, small occupied area, convenience for operation, and time and labor economization.