The effects of different compression ratios on engine performance were investigated on a single cylinder EGR engine by controlling the injection and ignition separately. Different turbochargers were matched to improve the full torque of each speed. The results show that the single cylinder EGR improves the fuel economy and NOx and CO emissions, but leads to the deterioration of THC emission and total power. Higher compression ratio can improve the engine thermal efficiency efficiently and reduce the fuel consumption, but too high compression ratio will increase the probability of engine knock and limit the torque of external characteristic. In the end, the torque at low speed improves by designing the turbocharger with a small turbine.