The controlling strategies of homogeneous charge compression ignition (HCCI) fueled by dimethyl ether (DME) and methanol were investigated. The experimental work was carried out on a modified single-cylinder diesel engine, which was fitted with port injection of DME and methanol dual fuel. The results show that exhaust gas recirculation (EGR) rate and DME percentage are two important parameters to control the HCCI combustion process. The ignition timing and combustion duration can be regulated in a suitable range with high indicated thermal efficiency and low emissions by adjusting the DME percentage and EGR rate. EGR cannot extend the maximum indicate mean effective pressure (IMEP) of HCCI operation range with dual fuel, but can enlarge the DME percentage range in normal combustion. The combustion efficiency largely depends on DME percentage, and EGR can improve combustion efficiency. The results also show that HC emissions strongly depend upon DME percentage, and CO emissions have good coherence to the peak mean temperature in cylinder. In normal combustion, adopting large DME percentage and high EGR rate can attain an optimal HCCI combustion. (C) 2006 Elsevier Ltd. All rights reserved.