Disposable adjustable injection device

The disposable adjustable injection device sequentially comprises an upper injection assembly and a lower injection assembly from top to bottom, the upper injection assembly comprises an upper cylinder body, a button assembly, a knob assembly, a dial and a power clutch mechanism, the lower injection assembly comprises a bottle assembly, a lower cylinder body and a needle head, and the needle head is installed at the bottom of the bottle assembly. A lower barrel is mounted on the outer side of the bottle assembly; a knob assembly is installed at the top of the upper barrel, a button assembly is installed at the top of the knob assembly, the knob assembly is connected with a power rod assembly on the inner side, and the power clutch mechanism comprises the power rod assembly, a screw assembly and a screw knob. The dosage can be automatically adjusted through the knob assembly and the dial, the piston can move up and down through the knob assembly and the power clutch mechanism by means of energy storage and rel