To evaluate the control efficiency of the bethylid parasitoids in suppressing wood-borer pests for biological application of the insect natural enemy group resources, the functional response of Sclerodermus sp., (Hymenoptera: Bethylidae) on 3rd instar larvae of Monochamus alternatus Hope (Coleoptera: Cerambycidae) was studied. A consummate evaluation system of control efficiency was established and its feasibility was clarified. The evaluation system consists of four parts: the standard of experimental insects, study on biological characters of parasitism behavior of the bethylid, the functional response of parasitoid and Zhongqi Index. The results indicated that one bethylid female could control 3-4 3rd instar larvae of M. alternates, the maximum quantity of hosts had been killed was 9.07 in 21days, the Sclerodermus sp. had great potential for control the wood borer pest. The result of parasitism functional response on one parasitoid wasp to different diversities of hosts was consistent to the host-searching efficiency and similar to the impact on the fecundity. Comprehensive evaluation indicated that the control efficiency of the bethylid on 3rd instar larvae of M. alternates was highest at 1:1 (releasing number property of parasitoid and its host), the Zhongqi Index was 39.63, which probably was caused by the bethylid's brood guarding behavior. That has certain similary with the observation on biological characters of parasitic behavior. Above all, the evaluation system is steadily, which could be used for biological control to screen out optimal parasitic wasp species for biological control application.