In this paper, a heat transfer in a high pressure ratio centrifugal compressor, which involves intense material temperature rise, is investigated. For such a compressor, it is required to predict impeller metal temperature under working condition for the life time estimation. Both Conjugate Heat Transfer (CHT) calculation and temperature measurement were conducted in the present study and the accuracy of CHT calculation was validated with experimental results. The mechanism of the impeller heating was considered through investigation into the CHT results. It was shown that imposing correct thermodynamic boundary conditions on impeller back surface is the most important in accurate temperature prediction with CHT calculation.