A bench comparative experiment of combustion and emission was carried out for a turbocharged natural gas engine with highpressure exhaust gas recirculation (HP EGR) and highlow pressure (HLP) EGR system respectively. Then the engine energy balance was quantitatively analyzed by the numerical simulation method and the influences of different EGR systems on fuel economy were investigated. The results of bench test show that the flame developing period and rapid combustion duration shorten, the combustion phase advances, and the peak values of incylinder pressure and heat release rate increase after using HLP EGR system. In addition, HC and CO emissions reduce, NO_x emission increases and the gas consumption rate reduces by 4.5% to 9.3%. According to the results of energy balance, the pumping loss, incylinder heat transfer loss and exhaust energy loss reduce and the reduction of exhaust energy was the largest. Besides, the friction loss increases.