Abstract: Developing new and highly efficient fuel additives have become an important topic of controlling engine combustion and emissions. For its unique physiochemical properties, nano-particles CeO2 makes it own a unique role in the field of catalytic combustion and exhaust gas purification. Through adding a trace amount of nano-particles CeO2 to diesel oil, two CeO2-diesel blends with the masse fraction of 50 and 100 mg/L of nano-particles CeO2 have been prepared, which makes D50C, D100C and Diesel these three test fuels, together with pure diesel as a reference. And the influences of these three test fuels on 186FA diesel engine combustion and emission have been investigated. The results show that: By using physical and chemical methods such as adding surfactant and ultrasonic processing, nano-particles CeO2 can be suspended stably in diesel. At full load at rated speed , the in-cylinder pressure peak, pressure rise rate peak and heat release rate peak have increased slightly when engine fuelled with D50C and D100C, while the corresponding crank angles are in advance accordingly, their ignition delay periods are also shorten by 1° or 2° crank angle accordingly. The engine's brake specific fuel consumption has reduced slightly with the effective thermal efficiency slightly increased when fuelled with D50C and D100C. Four conventional pollutants have reduced with different degrees with the addition of nano-particles CeO2 into diesel, and their reduction margins are more evident with the increase of the amount of nano-particles CeO2 in diesel. As compared to diesel, at full load at rated speed, the brake specific fuel consumption of D50C and D100C have droped 1.6% and 2.3% with a increase of 1.7% and 2.3% in corresponding effective thermal efficiency. The CO、HC、NOx and smoke emissions of D50C and D100C have decreased in average by 3.4% and 6.5%、15.1% and 18.4%、2.4% and 5.4%、4.0% and 7.8%, respectively. The costs of D50C and D100C blends are 0.8% and 1.6% higher than that of diesel. On the whole, with a slight increase in fuel price through the trace addition, nano-particles CeO2 is a kind of fuel additives with excellent performance, which can achieve highly combustion、energy conservation and emission reduction of engine.