[Objectives]  To improve the captive breeding of the wasp Tetrastichus septentrionalis, an important parasitic, biological control of Hyphantria cunea, by identifying the best hosts for the captive propagation of this species. [Methods]  The structure of the reproductive system and fecundity of adult female T. septentrionalis were studied by dissection. The effects of four different host species; H. cunea, Antherea pernyi, Tenebrio molitor and Zophobas atratus on the parasitism rate, eclosion rate, number of progeny per gram of host pupa, sex ratio and offspring body size of T. septentrionalis, were compared. [Results]  The female reproductive system consists of a pair of symmetrical ovaries, a pair of lateral oviducts, a common oviduct, an accessory gland, a spermatheca, a Dufour gland, venom reservoir and a venom glands. There are 10-12 ovarian tubes per female, and the number of eggs contained in each ovariole ranged from 3 to 8. Theoretically, the maximum number of eggs in each female ovary could reach 192 (there are 12 ovarioles in both the left and right ovaries and the number of eggs in each was 8). However, the maximum number of eggs actually observed was 145, and the mean number of eggs per female was 106. The optimal parasitoid-host ratios for T. septentrionalis were: 3︰1 for H. cunea, 100︰1 for A. pernyi pupae, 3︰1 for T.molitor pupae and 20 ︰1 for Z. atratus. The parasitism rate of T. molitor pupae and H. cunea pupae was significantly higher than that of A. pernyi and Z. atratus pupae. After five captive-bred generations, the highest parasitism rate (98.27%) was recorded in T. molitor pupae. The emergence rate of T. septentrionalis from T. molitor, H. cunea and A. pernyi pupae was > 97%. The highest T. septentrionalis emergence rate (98.26%) was also recorded in T. molitor pupae. The number of female wasps per gram of pupa was highest for A. pernyi (1 333), followed by T. molitor (781), and lowest for Z. atratus (217). The female: male sex ratio of T. septentrionalis was highest for T. molitor (7.65︰1), followed by Z. atratus (6.64︰1), and lowest for Z. atratus (4.69︰1). [Conclusion]  Although T. septentrionalis can successfully parasitize all four species of host pupae, Z. atratus pupae were significantly less suitable than those of the other three species. Host pupae should be chosen according to the demands of scientific research, the scale of production, and cost.