An exhaust gas purification system provided in a vehicle, comprising: a diesel particulate filter disposed in an exhaust pipe of an engine to collect particulate matter; an oxidation catalyst disposed in the exhaust pipe upstream of the diesel particulate filter; an exhaust pipe injector which injects fuel into the exhaust pipe upstream of the oxidation catalyst; an exhaust gas recirculation device that recirculates exhaust gas from an exhaust manifold to an intake manifold of the engine in accordance with an instructed exhaust gas recirculation opening; a variable nozzle turbocharger which performs turbocharging when a turbine disposed in the exhaust pipe and a compressor disposed in an intake pipe of the engine rotate integrally, a turbocharging amount of which can be adjusted using an actuator; and an intake throttle disposed between the turbocharger and the intake manifold to limit an intake air amount in accordance with an instructed intake throttle opening, characterized in that the exhaust gas purification system further comprises: a regeneration deceleration period intake/exhaust control unit that, when the vehicle decelerates by engine braking during regeneration of the diesel particulate filter, fully closes the opening of the exhaust gas recirculation device, fully opens the opening of the intake throttle, and increases the turbocharging amount of the variable nozzle turbocharger, and when the oxidation catalyst falls below the activation temperature, sets a temperature maintaining mode in which the amount of the opening of the exhaust gas recirculation device is increased and the amount of the opening of the intake throttle is decreased, and stops the exhaust pipe injection by the exhaust pipe injector. a diesel particulate filter disposed in an exhaust pipe of an engine to collect particulate matter; an oxidation catalyst disposed in the exhaust pipe upstream of the diesel particulate filter; an exhaust pipe injector which injects fuel into the exhaust pipe upstream of the oxidation catalyst; an exhaust gas recirculation device that recirculates exhaust gas from an exhaust manifold to an intake manifold of the engine in accordance with an instructed exhaust gas recirculation opening; a variable nozzle turbocharger which performs turbocharging when a turbine disposed in the exhaust pipe and a compressor disposed in an intake pipe of the engine rotate integrally, a turbocharging amount of which can be adjusted using an actuator; and an intake throttle disposed between the turbocharger and the intake manifold to limit an intake air amount in accordance with an instructed intake throttle opening, characterized in that the exhaust gas purification system further comprises: a regeneration deceleration period intake/exhaust control unit that, when the vehicle decelerates by engine braking during regeneration of the diesel particulate filter, fully closes the opening of the exhaust gas recirculation device, fully opens the opening of the intake throttle, and increases the turbocharging amount of the variable nozzle turbocharger, and when the oxidation catalyst falls below the activation temperature, sets a temperature maintaining mode in which the amount of the opening of the exhaust gas recirculation device is increased and the amount of the opening of the intake throttle is decreased, and stops the exhaust pipe injection by the exhaust pipe injector. a regeneration deceleration period intake/exhaust control unit that, when the vehicle decelerates by engine braking during regeneration of the diesel particulate filter, fully closes the opening of the exhaust gas recirculation device, fully opens the opening of the intake throttle, and increases the turbocharging amount of the variable nozzle turbocharger, and when the oxidation catalyst falls below the activation temperature, sets a temperature maintaining mode in which the amount of the opening of the exhaust gas recirculation device is increased and the amount of the opening of the intake throttle is decreased, and stops the exhaust pipe injection by the exhaust pipe injector.