A medical injection device, comprising: a housing having a first end cover and a second end cover provided at two ends thereof, respectively； a dial threaded rod, which is in threaded connected to the first end cover； and, a piston rod, which is used for expelling a dose, an upper end of the piston rod being connected to the dial threaded rod through a driving mechanism while a lower end thereof is in threaded connected to the second end cover. It further comprises a dosage adjustment mechanism, which is arranged between the dial threaded rod and the housing and used for driving the dial threaded rod to move in an axial direction of the housing.
