Abstract: Using in situ hybridization on tissue sections with DIG antisense RNA probe, the distribution of zebrafish (Danio rerio) nanos1 mRNA during oogenesis and spermatogenesis was detected, and the expression and function of nanos 1 during zebrafish gametogenesis was preliminarily studied. The results were as follows: nanos 1 mRNA uniformly dispersed throughout the cytoplasm of oocytes at all stages. Strong expression of nanos1 mRNA was observed in oogonia and stageⅠ、Ⅱ oocytes, but the signal became weaker in later stage oocytes. Strong expression of nanos 1 mRNA was detected in spermatogonia and relatively weaker signal was found in primary spermatocytes but no nanos 1 mRNA expression was observed in spermatids. The results suggested that nanos 1 may play an important role in maintenance and functioning of the germline stem cell—oogonia and spermatogonia.