Abstract: The infection and fatality ratio of Myzus nicotianae (Blackman) infected by Paecilomyces farinosus and Paecilomyces fumosoroseus were tested.The results showed that the Pf-27 strain of Paecilomyces farinosus and the Pf-30 strain of Paecilomyces fumosoroseus had better infection effects on tobacco aphid in 3 and 5 days after treatment, the indoor infected ratios of Pf-27 strains were 56.0% and 98.0%, and those of Pf-30 strains were 10.0% and 82.0%, respectively.10 days after spraying in tobacco fields with suspension of 1.5×10⁸ spores/mL, the infected ratio were 77.2% and 78.5% for Pf-27 strains and Pf-30 strains, respectively.It showed that the Pf-27 and Pf-30 strains are worth to further research.