The invention belongs to the technical field of packing equipment and relates to an automatic bag filling system comprising a bag supplying device, a bag suction device, a filling device and a bag sewing device which are connected in order. The bag supplying device comprises a bag supplying platform and a bag pushing mechanism located on the bag supplying platform. The bag suction device is located on one side of the bag supplying platform and comprises a bag feeding mechanism and a bag opening mechanism. A conveying mechanism is arranged below the filling device. The filling device corresponds to the bag suction device. The bag feeding mechanism and the bag opening mechanism comprise pick-up mechanisms used for sucking bag bodies. The pick-up mechanisms comprise box bodies with notches and pick-up members located in the box bodies and connected with power sources. Sawteeth used for grabbing and stabbing packing bag bodies are arranged on the pick-up members and stretch out from the notches to the outside. The structure is reasonable, the automation degree is high, and the production efficiency is high.