The invention relates to a high-precision pen-type 
injector which comprises an injection button, a 
dose adjusting knob, an engaging and disengaging 
ratchet, an engaging and disengaging spring, a spiral sleeve, a screw, a spiral 
ratchet, a fixed 
ratchet wheel 
assembly, a main body upper housing, a reset rotary knob, a reset spring, a 
cartridge case bin and a 
dose display sleeve. The screw is in threaded connection with a threaded hole of the spiral ratchet, a matched plane is arranged on the screw, the reset rotary knob is provided with a flat reset rotary knob hole matched with the screw, thereset rotary knob is installed on the screw through the reset rotary knob hole, a second one-way ratchet is arranged on the end face of the reset rotary knob, a first one-way ratchet matched with thesecond one-way ratchet is arranged on the fixed ratchet wheel 
assembly, one end of the reset spring abuts against the reset rotary knob, the other end of the reset spring abuts against the fixed ratchet wheel 
assembly, and the 
cartridge case bin is fixedly connected with the end of the main body upper housing. The high-precision pen-type 
injector saves effort in injection and is high in injectionprecision.