Abstract: Laboratory rearing and simulated field overwintering of Sphedanolestes impressicollis Stal were conducted in Beijing in 1991-1992. It has one generation a year and overwinters in 4 th instar in nymphal stage. The eggs aggregate in the form of egg masses, and hatch in 9.9+1.1 days after oviposition. There are 5 instars in nymphal stage and its development lasts for 315.0±4.9 days. The adults mate in 7~25 days after emergence and oviposit 22~23 days later. Not only its morphology and changes in color after moulting in all stages but also the bionomics were described. Experiments both in laboratory and in the field showed that it is a promising predator and can prey on Clostera anachoreta (Fabricius), Cnidocampa flavesccns (Walker), Nematus sp., Lymantria dispar (L.), Dendrblimus tabulaeformis Tsai et Liu, Malacosoma neustriatestacea Motschulsky,Aphis robi-niae Macchiati etc. many species of forest pests.