Several Cd 0.9 Zn 0.1 Te wafers with different properties are characterized by FTIR transmission. It is found that the IR transmission can be used qualitatively to deduce the quality of the Cd 0.9 Zn 0.1 Te wafers. The wafers with higher transmission have homogenized concentration distribution, lower dislocation density, and higher resistivity. According to the variation of IR transmission with wavenumber, IR transmission spectra can be classified into four types with different qualities. These results are initially analyzed based on the mechanism of Cd 0.9 Zn 0.1 Te IR absorption.