An exhaust gas purification system, which includes an engine and an exhaust pipe that is connected to an exhaust manifold of the engine, includes: a catalyst converter disposed at a rear side the engine on the exhaust pipe; a selective catalytic reduction on diesel particulate filter (SDPF) disposed at a rear side of the catalyst converter on the exhaust pipe; a reducing agent injector disposed between the catalyst converter and the SDPF on the exhaust pipe and injecting a reducing agent; and a controller controlling an amount of the reducing agent injected from the reducing agent injector.