Abstract: Bemisia tabaci (Gennadius) is an important insect pest in China and has developed high resistance to many kinds of insecticides. In this study, 8 strains of Metarhizium spp., isolated from different hosts obtained from various geographical locations were evaluated for their virulence against the 2nd instar nymphs of the “Q-biotype” B. tabaci. The results show that the M. flavoviride strain Mf96 had the highest virulence to the B. tabaci nymphs, with a corrected mortality of 89.5% at 7 d postr treatment and a LT₅₀ value of 3.65 d at the concentration of 1.0×10⁸ conidia/mL. With sprays at 4 concentrations (1.0×10⁸, 1.0×10⁷, 1.0×10⁶ and 1.0×10⁵ conidia/mL) of Mf96 conidial suspension, mortalities of the B. tabaci nymphs increased with treatment concentration and post-treatment time, and the LC₅₀ value was 1.20×10⁷ conidia/mL. Analysis of extracellular protease activities of the 8 strains reveals that enzyme activity (3.64 U/mL) of Mf96 was the highest among all the tested fungal strains. On SDAY medium, Mf96 showed such advantages as fast growth, quick germination and high sporulation, compared to other tested fungal strains. Therefore, Mf96 has a great potential in the biological control of the B. tabaci.