The invention discloses an abrasive automatic feeding device for feeding abrasives through mixing abrasive water jet forward. The device is mainly composed of a hopper, a jet flow pump, a high-pressure abrasive tank, a valve seat installed on the upper part of the high-pressure abrasive tank and a mixing cavity installed on the lower part of the high-pressure abrasive tank; the valve seat is connected with a sand adding pipeline, a high-pressure water pipeline, a low-pressure water pipeline and a safety valve; and the mixing cavity is also connected with the high-pressure water pipeline, an abrasive pipeline and an abrasive water jet flow pipeline. Each flow inlet and each flow outlet as well as each functional component are connected through high-pressure pipelines which are internally provided with high-pressure ball valves, throttling valves and pneumatic ball valves for controlling the pipelines; the jet flow pump is arranged between a feeding pump and the sand adding pipeline; and through the negative pressure effect of the jet flow pump, the abrasive adding operation of the high-pressure abrasion tank is realized. Through the connection and disconnection combination of the high-pressure ball valves, throttling valves and pneumatic ball valves, the device can respectively achieve the three kinds of operations including pure water jet flow, automatic feeding and abrasive water jet flow, is simple in structure, is convenient to operate, is safe and reliable, and can be widely applied to a forward mixing abrasion water jet flow generation system.