Abstract：Equilibrium partial pressures over Hg~1~-~xCd~xTe (MCT) melts have been considered as important thermodynamic parameters in high quality MCT crystal growth. However, these parameters reported until present in literatures are highly different from each other, which has become an obstacle to furthering studies on the crystal growth of MCT. This work determined systematically Hg and Te partial pressures over the MCT melts in the range of x=0-0.4, based on the principles of the optical absorption. Cd partial pressure is calculated from our experimental results and known thermodynamic data. Relationship between p~H~g and composition x is discussed. Comparison has been made between our results and other author's data. The cause of difference is pursued.