We report the study on Zn composition distributions in Cd0.96Zn0.04Te wafers grown in Shenzhou 3 spacecraft by micro-photoluminescence (μ-PL). The PL is performed over the crystalized " crust " region and the plateau regions in the " core " which are surrounded by non-crystalized solvent and resulted from incomplete melting of the raw material during the growth. Each PL spectrum has been fitted theoretically, resulting in the energy band gap Eg. The distributions of Eg are correlated to the Zn composition distributions. The results give out the variation trend and the statistical characteristics of the Zn composition distributions. An earth-grown CdZnTe wafer has been measured for comparison.