Combustion and emissions characteristics were investigated on a common rail turbocharged diesel engine operating in the composite combustion mode of Homogeneous charge of DME and diesel fuel injection. The results indicate that under a certain amount of premixing of DME with intake air, the maximum of cylinder pressure and pressure rise rate increase when the engine operating in the composite combustion mode. However, the moments of these are delayed compared with these of the diesel injection combustion mode. The peak of cylinder temperature is lower than that of the latter. The amount of heat release at the early stage is larger than that of the diesel injection mode.and the opposite at the later stage. The composite combustion mode is characterized by a three-stage combustion process, i.e., DME homogeneous compression combustion, the composite combustion of DME homogeneous compression combustion and the premixed combustion of diesel injection, and the premixed and diffusion combustion of diesel injection. When the engine operating in the composite combustion mode, NOx and Smoke emissions are reduced significantly. However, the increase of HC and CO emissions is observed. The exhaust temperature decreases. Key words-DME Homogeneous Charge Combustion Emissions