The utility model discloses a twin axle preprocessing device that sizes mixing, which comprises a slurry mixing barrel, variable frequency motor, first (mixing) shaft and second (mixing) shaft, the lower extreme of first (mixing) shaft and second (mixing) shaft all passes the mixing pulping barrel top cap, install the driving gear on the first (mixing) shaft, first axial -flow impeller and the first axial -flow impeller of going up, install driven gear on the second (mixing) shaft, axial -flow impeller and second axial -flow impeller on the second, the driving gear is meshed with the driven gear, driving gear and driven gear all are located outside the mixing pulping barrel, the first axial -flow impeller that goes up, first axial -flow impeller, axial -flow impeller and second axial -flow impeller all are located mixing pulping barrel on the second, the axial -flow impeller below just set up relatively on the first axial -flow impeller of going up was located the second, first axial -flow impeller is located second axial -flow impeller below and relative the setting. The utility model discloses a high dispersion and effective adhesion of medicament and ore particle can effectively improve sizing mixing and the flotation effect of particulate mineral.