Abstract: Objective Microarrays was used to text changes of gene expression of thymus cell in C57 mice one moth after exposed to 1 Gy γ-ray irradiation. Methods The difference of gene express between irradiated and un-irradiated mice being analysis by Agilent mouse oligo microarrays. Results In the observed 21319 known genes, 107 up-regulated at least 2-fold(13 excess 4-fold); whereas 9 genes were down-regulated 2-fold(2 more 4-fold). The function of theses genes are known as some basic metabolic process. Conclusions The gene changed in the experiment involved embryo development, organ formation and maintain, immunity or stress, protein compose, apoptosis, signal transduction. The number of gene is much more than that of down-regulated. It ought to be noticed that the gens which coding homy protein in embryo development, and aught also to be noticed that the gens which involve the function of PI3-K.