The invention discloses an incomplete gear mechanism which comprises a drive wheel and a driven wheel, wherein a location locking device used for reducing a gear mesh impact force and driven wheel angular displacement is arranged on two sides corresponding to a driven wheel locking arc section; location slots are correspondingly formed in two sides of the driven wheel locking arc section. In a high speed situation, the incomplete gear mechanism can overcome an inertia moment generated when the movement of the driven wheel is stopped, an impact force of gears and the angular displacement of the driven wheel are reduced; the phenomenon of blocking deadly is avoided; the location precision and the stability of the mechanism are improved.