Abstract: By comparison of sporulation and virulence, 29 strains of Beauveria bassiana isolated from Lepidopteran insects were screened for their pathogenicity to diamond moth, Plutella xylostella. Bb2390, a highly virulent strain was chosen, with LC₅₀ on the 2nd instar larvae at 1.56×10⁵ conidia×mL^-1, and LT₅₀ at 4.61 d under the concentration of 1.0×10⁷ conidia×mL^-1. The strain was pathogenic to all the stages of diamond moth, with mortality to eggs, 2nd instar larvae, pupae and adults were 37.2%, 90.3%, 58.8% and 24.5% respectively. The wettable powder of B. bassiana was used for field efficacy test against the larvae of P.xylostella, the control efficacy was 65.85%, significantly higher than aqueous conidial suspension with control efficacy 51.66%.