A portable inflator for tyre includes: a top cover, a bottom cover attached to the top cover, a pressure gauge, a switch and an accessories cover, the pressure gauge, the switch and the accessories cover being placed into the corresponding hole and trough which are defined in the top of the top cover and the bottom cover, an electric motor being placed inside the top cover and the bottom cover, supports pads being defined symmetrically at the inner walls of the top cover and the bottom cover, the pressure gauge connects with a cylinder cover by its connection module, the cylinder cover connecting with the integrative support cylinder by a seal part, a motor gear installed at the output shaft of the electric motor is mated with a gearing mechanism, the end of the gearing mechanism connecting with a piston by a piston shaft. The present invention adopts new materials and new process without increase of power, and can simplify structure on the basis of improving work efficiency.