On the basis of an in-depth analysis of the evaporation process of alloying elements during induction skull melting (ISM) amodel for the control mode of element evaporation has been established. The calculated results of Al element evaporation in Ti-48Al-2Cr-2Nb (at%) and Ti-24Al-11Nb (at%) alloys show that when melt temperature increases and/or pressure decreases, the controlmode of Al element evaporation changes from an evaporating reaction control mode at low melt temperature and/or under high outerpressure to a double control mode-evaporating reaction and liquid phase diffusion at high melt temperature and/or under low pressure. When the outer pressure is 133.3 Pa, the transformation temperatures of the control mode of Al element evaporation are approximately 1950 K and 2000 K respectively for the Ti-48Al-2Cr-2Nb (at%) and Ti-24Al-11Nb (at%) alloys. While the transformation pressures of the same alloys are approximately 133. 3 Pa and 66 Pa respectively when the melt temperature is 2073 K. Thereason is that the saturated vapor pressures of Al element in various alloys are different.