Micro-photoluminescence spectra of cadmium zinc telluride crystal at room temperature was tested by laser excited micro-photoluminescence spectroscopy.The Eg value of cadmium zinc telluride material was calculated by fitting the micro-photoluminescence spectra from the material band gap.According to the relationship between Eg and Zn composition derived from experiment data,the Zn composition was obtained with a self-developed program.The results was validated by X-ray double crystal diffraction.Experiment results prove that the Zn composition results by micro-photoluminescence is accurate and authentic.Therefore the room temperature micro-photoluminescence is an important test tool to measure the Zn composition in large scale fabrication.The Zn composition is an important basis for selecting the matching substrates in epitaxial HgCdTe film.That is helpful for studying and optimizing the growth of cadmium zinc telluride crystal.