The quenching-oil immersion method first developed in this work is an effective means of determining the homogenization temperature of melt inclusion in accessory minerals, and provides us with a new way to look into the temperatures in the initial stage of rock-forming process. In addition to the description of the new method, some applications are discussed in this paper. Good results have been obtained by using the new method to determine the rock-forming temperatures of some granites located in southern, southwestern and northwestern parts of China. The quenching-oil immersion method first developed in this work is an effective means of determining the homogenization temperature of melt inclusion in accessory minerals, and provides us with a new way to look into the temperatures in the initial stage of rock-forming process. In addition to the description of the new method, some applications are discussed in this paper. Good results have been obtained by using the new method to determine the rock-forming temperatures of some granites located in southern, southwestern and northwestern parts of China.