Abstract: The isothermal vapor-liquid equilibrium data for dimethyl ether-methanol-water ternary system were measured at 333.15 K，353.15 K,373.15 K and 393.15 K in a self-sucking type agitated static equilibrium cell.The effect of pressure and temperature on vapor-liquid equilibrium of dimethyl ether-methanol-water ternary system was analysed, the contents of dimethyl ether in vapor phase and liquid phase increased with increasing pressure, but decreased with increasing temperature.Thermodynamic calculation of vapor-liquid equilibrium data of dimethyl ether-methanol-water ternary system was carried out by using the method based on equation of state-activity coefficient,with PR equation for fugacity coefficients of vapor phase and NRTL equation for activity coefficients of liquid phase, and the calculated data were in agreement with the experiment data.