The present disclosure discloses an intake oxygen concentration control system suitable for an engine with lean NOx trapping technology. The system adopts an exhaust turbocharging device to provide a pressure difference for an oxygen-enriched membrane to generate oxygen-rich and oxygen-deficient gases, and controls the intake oxygen concentration of different cylinders by adjusting the opening of flow control valves to match lean and rich combustion cycles of a lean NOx trapping system. In a lean combustion cycle, all four cylinders are filled with an oxygen-rich gas, which can make the combustion more complete and improve the thermal efficiency and fuel economy. In a rich combustion cycle, one of the four cylinders is filled with an oxygen-deficient gas, and the other three cylinders are filled with air or an oxygen-rich gas with a low concentration, so that less fuel is required to create a reducing atmosphere to realize the release and reduction of NOx in a lean NOx trapping device, thereby reducing the fuel consumption and ensuring the output power of the other three cylinders.