Abstract: The invention provides a combined engine braking method and a turbocharging control device, including an air injection mechanism, through which air is injected into an engine (including into an exhaust flow passage downstream of an exhaust manifold of the engine, onto a guide gate provided in the exhaust flow passage, turbine blades of a turbocharger or an impeller of a compressor of the turbocharger), the operation of the turbocharger is controlled, and the airflow and the pressure of the engine are regulated. By the combined use of the turbocharging control device of the present invention and an engine braking device, a high-performance combined engine braking method is realized. The system of the present invention is compact in structure, of a small volume and can be arranged on the upstream of the turbine or on the turbocharger to make full use of the turbocharger, thereby reducing turbo lag, increasing exhaust gas circulation, reducing engine exhaust emission and increasing engine braking power.