〔Abstract〕 Objective To explore the localization and expression of nanos1 gene in Schistosoma japonicum at different developmental stages.Methods The nanos1 gene of Schistosoma japonicum was searched in NCBI, amplified by PCR and analyzed by BLAST software. DNAMAN 6.0 and ClustalX 2.0.9 were used for multiple sequence alignment, and MAGA 5.05 was used to construct phylogenetic tree for phylogenetic analysis. Digoxin(DIG) labeled RNA probes were transcribed in vitro and used for whole mount in situ hybridization to determine the localization of nanos1 gene in Schistosoma japonicum at 3 developmental stages: 18, 24 and 42 days.Results The nanos1 gene of Schistosoma japonicum was amplified by PCR. Bioinformatics analysis showed that the highest homology was found between its coding protein and nanos2 protein of Schistosoma mansoni. RNA probes were successfully transcribed in vitro for whole mount in situ hybridization of Schistosoma japonicum at different developmental stages.Positive signals were detected in the ovaries and vitellarium of 24-day-old and 42-day-old females,and in the ovaries of 18-day-old females. No significant positive signal was observed in males at all developmental stages. Conclusion Nanos1 gene is highly expressed in the ovaries and vitellarium of 24-day-old and 42-day-old females,and in the ovaries of 18-day-old females,but no significant positive signal is observed in males at any developmental stages. The expression pattern of nanos1 gene in Schistosoma japonicum is observed successfully,which provided an important clue for studying the function of nanos1 gene.