On the basis of the characteristics of homogeneous charge compression ignition (HCCI) combustion and in-cylinder direct injection (DI) combustion for a diesel engine fueled with dimethyl ether (DME), a new combustion concept, namely, low-temperature combustion (LTC) of compound charge with port aspiration and in-cylinder DI of DME, is proposed. A diesel engine is modified to carry out this test. The combustion and emission characteristics are investigated with the variation of fuel mass via air intake port at different engine loads. The results show that the LTC process comprises HCCI combustion and the diffusion combustion and prove that LTC is an effective method to suppress NOx formation. In comparison to the DME HCCI combustion mode, DME LTC can extend the engine-operating range with little change in NOx emissions and a considerable reduction in HC and CO emissions.