The invention aims at providing a supercharged diesel engine EGR realization device based on an auxiliary turbosupercharger. The supercharged diesel engine EGR realization device comprises a main turbosupercharger and the auxiliary turbosupercharger; an exhaust manifold is divided into a main exhaust manifold part and an auxiliary exhaust manifold part; the main exhaust manifold part is connected with a turbine of the main turbosupercharger; the auxiliary exhaust manifold part is connected with a turbine inlet of the auxiliary turbosupercharger and the atmosphere; an air inlet manifold is connected with a gas compressor of the main turbosupercharger and a gas compressor of the auxiliary turbosupercharger; a gas compressor outlet of the main turbosupercharger is connected with a turbine inlet of the main turbosupercharger; and a gas compressor inlet of the auxiliary turbosupercharger is connected with a turbine outlet of the main turbosupercharger and the atmosphere. Exhausted gas at the rear part of the turbine of the main turbosupercharger can be pressurized in an EGR mode to allow the exhaust pressure of the rear part of the turbine to be higher than the intake pressure, so that EGR is realized, in the meanwhile, in a non-EGR mode, the auxiliary turbosupercharger can boost a part of air, and the quantity of fresh air in the air inlet manifold is increased.