The utility model discloses a be applicable to variable rate fertilizer applicator's fertilizer mixing device, belong to the agricultural machine field. Its characterized in that contains one -level mixing chamber, connector, second grade mixing chamber, auger delivery blade axle, motor power 1, motor power 2, gear 1, gear 2, leaks fertile mouthful and bearing etc. And wherein, the terminal head end with second grade mixing chamber in one -level mixing chamber passes through the connector to be connected, and the variable rate fertilizer applicator frame is fixed in in one -level mixing chamber, and rotate under motor power 1's drive in second grade mixing chamber, auger delivery blade axle is installed at one -level mixing chamber and second grade mixing intracavity, and auger delivery blade axle rotates under motor power 2's drive, realizes the second grade and mixes the mixed cropping industry. This fertilizer mixing device has realized the homogeneous mixing of multiple fertilizer, can effectively avoid the layering segregation phenomenon of mixing fertilizer, has improved the utilization ratio of fertilizer.