The invention provides a single cylinder diesel EGR device based on high-pressure air two-stage supercharging and a control method. The single cylinder diesel EGR device comprises an air inlet three-way valve, an exhaust three-way valve, a bypass valve, a one-way valve, an electromagnetic control valve, a first turbocharger, a second turbocharger, a waste gas pressure-stabilization tank, an EGR cooler, a temperature sensor and a flow meter. According to the single cylinder diesel EGR device, the two turbochargers in series connection are controlled so that two-stage supercharging of EGR waste gas can be achieved through high-pressure and high-speed compressed air, the problem of EGR waste gas backflow under different air inlet pressures, especially high air inlet pressure is effectively solved, and meanwhile the requirements for EGR adjustment under different medium, high and low work conditions can be met. The single cylinder diesel EGR device is particularly suitable for marine diesel engine energy saving and emission reduction or single cylinder diesel testing places or other place.