An experimental study on blended combustion for dimethyl ether (DME) with diesel was carried out for a 4-cylinder diesel engine. DME was premixed with air through a mixer and then was entered the cylinder. Diesel was supplied by original fuel system. The experimental results show that the autoignition is advanced with more DME and the preignition is obvious, which leads to the engine operation roughness and combustion deterioration. When the ignition inhibitor (LPG) added into DME is exceeded 30%, it can retard the autoignition and control the start of combustion effectively.  