The toxicity bioassay of Beauveria bassiana Vuillemin MZ041016 to Phenacoccus solenopsis Tinsley during four different concentrations on 2.0×105, 2.0×106,2.0×107,2.0×108 spores per mL was measured by topical application in laboratory, and 1st，2nd, 3rd of larvae and female adults of P.solenopsis were vaccinated respectively．The results indicated that the virulence of B.bassiana MZ041016 to P.solenopsis was high．The accumulative mortality was highest in concentration of 2.0×108 spores per mL. The median lethal concentration of 1st，2nd, 3rd of larvae and adults of the P.solenopsis was (2.10±0.06)×106,(2.43±0.06)×106,(3.20±0.06)×106,(3.54±0.06)×106 spores per mL respectively; the median lethal time was (4.52±0.17),(5.34±0.51),(6.12±0.35),(6.48±0.32) d respectively．