The invention aims at providing a three-
turbocharger three-stage sequential turbocharging device with an EGR achieving function and a three-
turbocharger three-stage sequential turbocharging control method with the EGR achieving function. The sequential turbocharging device comprises an exhaust header, an air-intake header, a first big
turbocharger, a second big turbocharger and a small turbocharger, wherein the inlet end of a first
turbine communicates with the exhaust header, the inlet end of a second
turbine communicates with the exhaust header, the inlet end of a small
turbine communicates with the exhaust header, and the outlet end of the first turbine, the outlet end of the second turbine and the outlet end of the small turbine all communicate with an exhaust header
pipe; and the inlet end of a first
air compressor, the inlet end of a second
air compressor and the inlet end of a small
air compressor all communicate with an air-intake header
pipe, and the outlet end of the first air compressor, the outlet end of the second air compressor and the outlet end of the small air compressor all communicate with an air outlet header
pipe. According to the three-turbocharger three-stage sequential turbocharging device and control method with the EGR achieving function, the effect of performing sequential turbocharging to improve the low working-condition performance of a
diesel engine can be achieved, the
NOx exhaust requirement of the
diesel engine in an exhaust
control area can be met through EGR, and the comprehensive performance of the
diesel engine can be greatly improved.