The invention relates to a high-precision pen-type injector, which includes an injection button, a dose adjustment knob, a clutch ratchet, a clutch spring, a spiral sleeve, a screw rod, a spiral ratchet, a fixed ratchet assembly, a main body upper shell, a reset knob, a reset spring, The drug silo and the dose display sleeve, the screw is threadedly connected with the threaded hole of the helical ratchet, the screw is provided with a matching plane, the reset knob is provided with a reset knob hole that is flattened with the screw, and the reset knob passes through the reset knob The hole is installed on the screw rod, and the end face of the reset knob is provided with a second one-way ratchet, and the fixed ratchet assembly is provided with a first one-way ratchet cooperating with the second one-way ratchet, and one end of the return spring is connected with the reset knob Against each other, the other end is against the fixed ratchet assembly, and the drug silo is fixedly connected to the end of the upper shell of the main body. The invention saves injection effort and has high injection precision.