The purpose of this study was to investigate the effect of the ethanol fraction on the combustion and exhaust emissions characteristics of dimethyl ether (DME)-ethanol dual-fuel reactivity controlled compression ignition (RCCI) engine. In this study, a modified single-cylinder diesel engine was used. The main parameters of this study were the in-cylinder injection timing of DME and the ethanol fraction. The ethanol fraction was found to have a more obvious effect on the indicated mean effective pressure (IMEP) for advanced in-cylinder injection timings than around the top dead center (TDC) conditions. For the same ignition timing, the ethanol fraction had little influence on the IMEP. Increasing the ethanol fraction induced an increase in combustion duration and a decrease in premixed combustion duration (CA10-CA50) around the TDC injection condition. The effect of ethanol on P-max was insignificant for CA50. The application of the DME-ethanol dual-fuel combustion strategy caused a significant reduction of ISNOx without deterioration of ISsoot. In addition, a high ethanol fraction led to a low ISNOx for the same premixed combustion duration. The ISHC and ISCO emissions increased slightly with increasing ethanol fraction for DME-ethanol dual-fuel combustion. However, the emissions from DME-ethanol combustion were lower than those obtained previously with biodiesel-ethanol and diesel-ethanol dual-fuel combustion. (C) 2016 Elsevier Ltd. All rights reserved.