Abstract: Conidial suspension(5×10⁶conidia·ml^-1) of the entomopathogenic fungus,Beauveria bassiana BBSG8702 was used to inoculate newly emerged apterous adults of the green peach aphid (Myzus persicae) on detached cabbage leaves in order to measure time-specific infection rate of the fungal agent. The aphids of conidia attached were disinfected using0.2% chlorothalonil solution at intervals of 8～56 h after inoculation and then maintained at 10 and 20℃ for daily observation. There was a significant difference (P<0.05) in mortality attributed to the fungal infection among the time intervals within56 h at 10℃ after inoculation or within40 h at 20℃.Compared with the control (not treated with 0.2% chlorothalonil after inoculation),time-specific infection rate at 10℃ was estimated as 22.9%,48.8%,64.9%,80.4%,72.7%,and 98.3% within8 h,16 h,24 h,32 h,40 h,and 56 h after inoculation, respectively. The same estimates at 20℃ were 31.6%,48.8%,58.6%,86.9%, 97.2%,and 98.7%, respectively. The results indicate that the first 24 h after inoculation was crucial to the infection of B. bassiana to M. persicae. Effective infection with the first 24 h accumulated to 59～65% at 10～20℃.