Abstract: The biological characteristics of Euplectrus laphygmae Ferrière, which was a gregarious ectoparasitoid of the larvae Spodoptera litura (Fabricius), were studied in this paper. The results showed that the largest numbers of eggs laid by one female E. laphygmae was 139, and the average numbers was 73.69 in the laboratory. E. laphygmae female laid 1―5 eggs on one individual S. litura larvae (sometimes 6―9 eggs), the eggs were laid on the back of the 1―4 abdominal segments mostly, with fewer on the lateral side and none on the venter. E. laphygmae mostly parasitized the 2nd, 3rd instar larvae of S. litura, in which early 3rd instar larvae were most preferred host, with the preference index was 0.65 and the developmental duration from egg to adult was 9.93±0.19 days.