Abstract: The influence of the isobutanol-diesel mixing ratios on the engine combustion process and performance was investigated by turbocharged and intercooled common rail diesel engine.The results showed that under the same load，the fuel heating value is reduced as the increase of mixing ratio，while the fuel consumption is increased； after blending isobutanol，the oxygen content is increased，which can inhibit soot emission effectively，but the cetane number is decreased.At the working conditions of ESC-13，the fuel with 10% isobutanol generates the lowest soot weighting specific emissions.Under the same speed and small load conditions，increasing the mixing ratio has a trend of increasing the latent heat of vaporization of the fuel，and with a lower octane number，causing the prolonged ignition delay of the fuels and lower cylinder temperature and more the CO，HC and particulate emissions.While the higher cycle heat in cylinder under large load working conditions can effectively restrain the trend，except for the NOx emission，the rest of the harmful specific emissions are lowered.

Key words: isobutanol-diesel, blending ratio, turbocharged diesel engine, performance