DIESEL ENGINE EXHAUST GAS PURIFICATION METHOD AND EXHAUST GAS PURIFICATION SYSTEM

An exhaust gas purification method of a diesel engine, which purifies exhaust gas while suppressing deteriorations in drivability and fuel consumption, when the exhaust gas G enters a rich reduction state, opens an EGR valve 15 and closes an intake throttle 6 if a temperature of the NOx occlusion reduction catalyst 11 is at or above a predetermined temperature and a vehicle mounting a diesel engine 1 is decelerating from a speed at or above a predetermined speed, and then closes an exhaust throttle 20 provided downstream of the NOx occlusion reduction catalyst 11 and supplies fuel to the NOx occlusion reduction catalyst 11 as a reductant.