Abstract: To provide references for development and production of microbial inoculum, the Bt.DBW902 strain with high toxic to Plutella xylostella (L.) was used to establish the optimal fermentation condition and explore the preparation technics of Bt powder. Survival strains, viable spores and protein content were used as indexes, the fermentation condition was optimized by adopting a single-factor assay. The original types of Bt powder were prepared by adding different mineral with different concentrations, then the powder characteristics were detected. Results showed that the optimal fermentation condition was as follows: inoculum quantity 2%, seed age 10 h, agitation speed 200 r/min, initial pH 7.0-7.5, temperature 30℃ and culture time 48 h. Under this fermentation condition, the viable cells could reach 2.99×10⁹ CFU/mL, viable spores could reach 8.88×10⁸ CFU/mL and crystal proteins could reach 20.0 mg/mL. In the original types of Bt powder, the artificial zeolite could best protect the Bt powder, and the 1.0%-3.0% dose of artificial zeolite had the strongest effect on P.xylostella. This study optimized the fermentation condition of Bt.DBW902 and obtained the original types of Bt powder which laid the foundation for development and research of Bt powder.