A fuel reforming system includes: an engine combusting reformed gas to generate mechanical power; an intake line connected to the engine to supply the reformed gas and air to the engine; an exhaust line connected to the engine to circulate the exhaust gas discharged from the engine; a fuel reformer provided at an exhaust gas recirculation (EGR) line diverging from the exhaust line; and a catalyst disposed at the exhaust line and purifying nitrogen oxide included in the exhaust gas at a front end of the fuel reformer. In particular, the fuel reformer mixes the fuel with the EGR gas which is a part of the exhaust gas and passes through the EGR line, and reforms the fuel mixed in the EGR gas.