In this paper, the relationship between the nematode, Steinernema fetine(Fillpjev) Agriotos strain and 3rd -instar larvae of the striped flea beetle, Pkyllotreta striolats(Fabr. ), was simulated with Hassell-varley model and Holling' s functional response model. It showed that during 48 hours the maximum number of hosts that the nematodes could parasite was 72 3rd-instar larvae under the most suitable condition ; the interference constant of the nematodes was 0. 2738. The results of host age susceptibility tests showed that susceptibility to the nematodes increased with age of the host.