To select efficient entomopathogenic fungal strains of Lecanicillium for the biocontrol of aphid, Myzus persicae, conidial suspension (1 × 10 ⁷ conidia/ml) was sprayed onto a detached Chinese cabbage leaf in a petri dish with a dampened filter paper that had 20 nymphs of aphid. Lecancillium strain 4078 and 6543 were the best strains for the biocontrol of aphid at high temperature of 30 oC and low relative humidity (RH) of 85%, respectively. The cumulative mortality of strain 4078 at 30 oC after 3 days was 100% and that of strain 6543 was 90% at 85% RH after 5 days. Strain 4078 also exhibited almost 100% germination ratio of conidia and high rate of mycelial growth at the broad temperature-range of 15~25 oC. The strain 4078 and 6543 were all identified as Lecanicillium species based on the DNA sequences (accession no.: EF026004 and EF026005, respectively) of the ITS regions of the fungi. Excellent production of aerial conidia of strain 6543 was accomplished by using steamed polished rice as the solid culture medium.