The invention relates to an automatic quantitative down-filling machine, which comprises a rack, a table surface, a balance, a down tube, a tube cover, an elbow, a hose, a down-filling gun and an automatic control device. The down-filling gun consists of a connecting pipe, an air amplifier, an air amplifier fixing cover, a down-filling pipe and a down-filling gun handle, the automatic control device comprises a down-filling switch, a weighing sensor, a single-chip microcomputer and a solenoid valve; the balance is arranged on the table surface, the down tube is supported on the balance by a bracket and is provided with a down-adding port, the hose is connected with the tube cover through the elbow, an elbow clamping block is fixed on a crossbeam, the down-filling gun is connected with thehose through the connecting pipe, the down-filling switch is arranged on the down-filling gun handle, an air intake pipe connector is connected with the air amplifier in the down-filling gun, and an air intake pipe penetrates through a hole on the down-filling gun handle and is connected with the air intake pipe connector. The invention has the advantages that the quantitative weighing and pneumatic filling of down are realized with the automatic control technology, the down-filing amount can be arbitrarily set, the filling efficiency is high, the working environment is good, and the down waste and damage can be reduced.