An injection pen capable of fine adjustment, comprising: a differential spiral transmission mechanism, comprising a push rod (18), a push rod nut (22), a positioning rotary ratchet (21), an adjustment rod (17), and a ratchet tube (8)； a dose adjustment mechanism, comprising a knob (2), a numerical code tube (15), an adjustment tube (7), a ratchet connection ring (9), and an adjustment and connection tube (6)； a housing (3), the differential spiral transmission mechanism being provided in the housing (3), a window (4) being provided on the housing (3), and a pen core holder (24) being provided in the housing (3)； and an injection mechanism, comprising a button connection member (16), a button (1), and a button spring (14). During adjustment, a contact portion between the ratchet connection ring (9) and the ratchet tube (8) clicks under the action of the ratchet so as to prompt a user. In addition, a visual prompt on the window (4) also facilitates the adjustment of a dose. The injection pen capable of fine adjustment can also be reused, and can improve injection precision by converting a spiral motion into a linear motion.
