In this paper, the injection rates and fuel line pressure of DME and diesel are measured. The effects of fluid properties on the injection characteristics in a common rail injection system are investigated. The results show that the injection timing of DME begins and ends later than that of diesel due to larger compressibility. The peak injection rates of DME and diesel are similar. The injection quantity of DME is larger than that of diesel, while its injection energy is lower. Compared to diesel, the fluctuation amplitude of DME during injection is smaller, and the duration is longer.