Objective To identify the molecular evolution of Miox and its temporal and spatial expression patterns in the evolution of Xenopus laevis embryos. Methods The temporal and spatial expression patterns were analyzed by semi-quantitative reverse-transcriptional PCR (RT-PCR) and whole-mount in situ hybridization, respectively. Results We investigated the temporal expression pattern of Miox during embryogenesis of Xenopus laevis by RT-PCR and found that hardly any expression was detected before stage 26. Miox firstly expressed at stage 28 with a very small amount. Its expression level gradually increased along with the development of the process and reaced its peak at stage 40 and kept a high stable level in later period. Compared with stage 28,34,the expression of stage 40,41,45 were upregulated significantly(P＜0.05) .Compared with stage 40,the expression of stage 41 was upregulated markedly(P＜0.05).But compared with stage 41,the expresssion of stage 45 was downregulated(P＜0.05).The results of whole-mount in situ hybridization showed that Miox started express at stage 33 and the expression trend was consistent with RT-PCR. We also found that Miox only expressed in the pronephros tubules in the whole procss of embryo development. Conclusion Miox was tissue-specific in Xenopus laevis pronephros development, which may provide a marker for later pronephros development in the study of organogenesis.