The invention discloses a full-automatic micro counter weight material sorting device which comprises a primary conveying belt, a secondary conveying belt, monomer weighing units, automatic baffle plates, discharge ports and a computer controller; the number of the monomer weighing units is more than six; the monomer weighing units are uniformly distributed on the two sides of a conveying surface of the primary conveying belt, and are connected with the computer controller; the secondary conveying belt is connected with the primary conveying belt end to end; the number of the discharge ports is more than two; and the discharge ports are fixed to a secondary conveying belt bracket, and are uniformly distributed on the two sides of a conveying surface of the secondary conveying belt. According to the full-automatic micro counter weight material sorting device, operating personnel firstly set standard weight of a package on the computer controller and then place materials on all the monomer weighing units, the computer controller works out the sum of the weight of the materials on several monomer weighing units, which is closest to the set standard weight, and then controls to start conveying belts of the corresponding monomer weighing units, and the materials are conveyed to the primary conveying belt for packing subsequently.