The invention discloses an automatic charging tray feeding system. The system comprises a rack, a conveying belt, an assembling positioning mechanism, a material waiting position, a stock bin and an electric control box, the stock bin, the material waiting position, and the assembling positioning mechanism are arranged from back to front sequentially in the conveying direction, the assembling positioning mechanism comprises a lifting air cylinder, a lifting plate, a positioning air cylinder and positioning clamping claws, a piston rod of the lifting air cylinder is connected with the lifting plate, a charging tray is lifted to the positioning face, the two positioning clamping claws limit the charging tray to the position over the conveying belt, the stock bin comprises a discharging frame, a lifting mechanism and a dividing clamping claw, the lifting mechanism lifts the bottom charging tray to the conveying belt, and the dividing clamping jaw lifts remaining charging trays. Continuousfeeding can be ensured, the feeding position precision is greatly improved, the correcting rate of the next procedure can be ensured, the whole structure is ingenious and fine, in combination with sensors of mechanisms, the feeding process automation is achieved through a PLC, the labor intensity of a worker is greatly reduced, production cost is reduced, and production efficiency and productionprecision are improved.