Based on data from systematic investigation of 3 outdoor st ored bulk grain masses in Jingmen City, Hubei Province (112°07′E, 30°02′N) i n 1992, insects of 37 species were identified with two classes, seven or ders, twent y-six families. Twenty-six beetles are main species accounting for 64.7% of t h e community. Superiority index estimation indicated that the Crptolestes ferru gineu s(Stephens), Cryptolestes minutus（Oliver) and Rhizopertha dominica Fa b. were the most destructive pest in outdoor stored bulk grain mass. In spring, the spe c ies diversity, abundance, evenness and the population size in the community incr ease. In July, however, the species diversity and evenness maximize. The insect communitvy is low in stability and diversity in the surface layer. In the bottom layer, however, species diversity and stability is higher.