This paper deals with the biology and ecology of Microplitis prodeniae (Viereck), a dominant braconid wasp parasited on Spodoptera litura Fabricius, one of the most important pests in tobacco fields. The wasp has two climaxes on population dynamics, one of which occurs at the last ten day of April and the other occurs at the mid - ten day of June, which can control its host in some degree. It emerges normally all day long at 24 [approximately equal] 28[degree]C and 75 % [approximately equal] 85 % RH. But the emergence chiefly occurs at 4 [approximately equal] 6 am. The quantity of female wasp is more than that of the male' s in the natural condition. The average sex ratio of the wasp is 2. 30 :1, The adult fed by nutrition expecially 25% solution of glucose can prolong their longevity significantly and the condition with higher hunidity is also beneficial to the adult survival. The equation between its longevity and hunidity can be described as y = 13. 759 7 + 0. 155 1 x. The relations between development duration and temperature from the stage of parasitism to incunabulum and incunabulum to emergence can be described as N = 134.0426/(T -9.5234) and N =84.9558/(T - 11.5965), respectively, the results of which fit in with X2 test. Life cycle and development; Parasites diseases and disorders; Parasites; Insect parasites; Hosts; Insect hosts; Ecology; Population dynamics; Population structure Spodoptera litura (Noctuidae); Hymenopteran parasites; Microplitis prodeniae; Parasite biology & ecology Microplitis prodeniae (Braconidae); Development; Lepidopteran hosts; Spodoptera litura; Parasite biology & ecology; Ecology; Population sex ratio none