The utility model relates to an automatic accelerator system of a lorry-mounted crane. Wherein a multi-way valve (2) is arranged beside the operating component (1); a port P and a port LS are formed in the multi-way valve (2); the P port is connected with a pressure detection unit A (3); the LS port is connected with a pressure detection unit B (4), a control unit (5) is connected beside the pressure detection unit A (3) and the pressure detection unit B (4), an engine (6) is arranged beside the control unit (5), the engine (6) is connected with the multi-way valve (1), and a control loop is arranged between the engine (6) and the multi-way valve (1). The system automatically controls the rotating speed of the engine, so that the flow of hydraulic oil passing through the multi-way valve meets the saturation flow required by the crane in various working modes, the maximum utilization rate of the flow of the hydraulic oil in the working process of the crane is finally achieved, energy conservation and emission reduction can be achieved, operation is simplified, and the working speed of the crane is increased.