Abstract: Laboratory screening and selection of Beauveria bassiana against peach fruit borer, Carposina nipponensis, were carried out in Beijing during 1988-89. Seventy strains were collected from Liaoning, Henan and Shandong Provinces and were inoculated on the 3rd instar larvae of C. nipponensis. Three strains selected (46-1, 46-2 and 37-3) had infectivities of 96.7%, 92.8% and 93.3%, respectively, which were higher than that of other strains. The growth character and chitinase activity of the collected B. bassiana strains were studied with four strains representing high, medium, and low toxicities to the host insect. The results indicated that the infectivity of B. bassiana strains tested had a significant positive correlation with the quantity of mycelia growth, chitinase activity and spore productivity.