Abstract: In this paper, the boiling points of methyldichlorosilane-methyltrichlorosilane-toluene system and of the three binary systems are determined at 101.3 kPa with a new type of magnetic pump-ebulliometer.The VLE data of the three binary systems, respectively,are correlated with the Margules, van Laar, Wilson, and NRTL equations. The equilibrium composition of the vapor phase of three binary systems are calculated from TPX by indirect method. Activity coefficients are calculated after accounting for the nonideality of the vapor phase. The model parameters of liquid activity coefficient are correlated by the least square method. The vapor pressure of the pure components are obtained by using Antoine constants from the literature. The VLE data of ternary system are predicted by the Wilson equation. The calculated boiling points show good agreement with the experimental data.