Abstract: Virulence of Beauveria bassiana (Fungi: Hyphomycetes) against the green peach aphid, Myzus persicae (Homoptera: Aphididae) was examined at 28, 21, 16 and 11℃ in the laboratory. A time dose mortality model was used for analyzing the mortality rates as affected by temperature. The results showed that aphids had higher mortality rates at 28 and 21℃ than those at 16 and 11℃. With a concentration of 10⁷ conidia/ml, aphids incubated at 28 and 21℃ started to die on the 3rd-4th day and all aphids died on the 6th day. However, aphids tested at 16 and 11℃ began to die on the 6th and 11th day and did not suffer more than 90% mortality until the 10th and 20th day after inoculation. The cumulative mortality rates of the aphids at 21℃ was higher than that at 28℃. With a concentration of 10⁶ conidia/ml, the LT₅₀ of M.persicae at 21, 28, 16 and 11℃ was 3.7, 5.1, 9.2 and 18.7 d respectively.