Explosion limits of DME-Air and DME-O_2 premixture is investigated experimentally using a rapid compression-expansion machine. Combustion experiments are carried out at the constant surrounding pressure with changing the compressed gas temperature at TDC. Then, representative temperature is the temperature at the center of combustion chamber measured by a thin Pt resistance wire thermometer having a diameter of 15μm. The experimental result show that explosion limits are not depended on both of equivalence ratio and compression pressure, and only depended on temperature above a pressure of 1MPa. Also, it shows that autoignition temperature of DME-Air premixture is 560K above a pressure of 1MPa.