Objective:To study the dynamic expression of male sterility related gene Boule in the first spermatogenesis wave of mouse testes as well as the function of Boule during spermatogenesis. Methods: The expression level of BOULE protein in various tissues and time points were examined using Western blotting. Real-time PCR was used to establish the Boule mRNA expression profile after birth. Immunohistochemistry and immunofluorescence were carried out to analyze the expression and distribution of BOULE protein in mouse testes. Results: Western blot confirmed the specific expression of BOULE protein in mouse testes. Real-time PCR showed that Boule mRNA was first detectable in the testis of mice 20 days after birth. Immunohistochemistry showed that BOULE protein located in the cytoplasm of pachytene spermatocyte and round spermatid during spermatogenesis. Immunofluorescence witnessed the BOULE granule,which formed in the cytoplasm. Conclusion: Boule expression is precisely regulated during spermatogenesis. The specific expression in the cytoplasm of spermatocyte and round spermatid suggested that Boule may be important for spermatocyte progressing and round spermatid differentiation.