Abstract: To investigate the function of the nanos1 gene in the reproductive development of Macrobrachium rosenbergii, we cloned its nanos1 gene. The cDNA sequence was 2 811 bp, encoding 243 amino acids. Phylogenetic analysis shows that it had the highest homology with Eriocheir sinensis, higher homology with nanos1 in fish but lower homology with mammals. We detected the expression level of the gene at different embryonic developmental stages and in larvae by real-time fluorescence quantitative PCR. The results show that the expression level of nanso1 mRNA was the highest at unfertilized stage, significantly higher than that at fertilized stage and the other embryonic developmental stages (P<0.05). During the embryonic development, the expression was the highest at fertilization stage, significantly higher than that at cleavage stage and very significantly higher than that at late embryonic development (P<0.01). The expression level of this gene at cleavage stage was significantly higher than that from blastocyst stage to larval stage. The expression level from blastocyst stage to larval stage was low and there was no difference.In situ hybridization shows that nanos1 mRNA was expressed in the cytoplasm of oocytes and primary oocytes (Oc1, Oc2, Oc3 and Oc4). The results show that nanos1 is closely related to the development of female germ cells of M. rosenbergii.