Exhaust gas purification system

Provided is an exhaust gas purification system with which it is possible to prevent a decrease in engine torque during a desulfurization process in a NOx storage reduction catalyst. This exhaust gas purification system is equipped with a NOx storage reduction catalyst (3) provided in the exhaust pipe (2) of an engine (E), and a desulfurization process control unit (8) that controls the intake air amount for the engine (E) to enrich the exhaust gas, and performs a desulfurization process in the NOx storage reduction catalyst (3). The desulfurization process control unit (8) is constructed so as to gradually reduce the intake air amount when the desulfurization process begins.