The sex pheromone blend of a China strain of the black cutworm moth Agrotis ypsilon (Rottemberg) (Lepidoptera: Noctuidae) was investigated. Chemical analysis of pheromone gland extracts of 3-day-old females showed that individual isolated glands contained only very small amounts of pheromone. The high-resolution gas chromatography combined with mass spectrometry (GC-MS) analysis showed the presence of Cis-7-dodecenyl acetate (Z7-12:Ac, A), Cis-9-tetradecenyl acetate (Z9-14:Ac, B), Cis-11-hexadecenyl acetate (Z11-16:Ac, C), Cis-8-dodecenyl acetate (Z8-12:Ac, E) and Cis-5-decenyl acetate (Z5-10:Ac, D) in biologically active pheromone gland extracts. An extract of one gland from a day 3 female gave the following values for the gland components: 0.245±0.098 ng for Z7-12:Ac, 0.080±0.031 ng for Z9-14:Ac, 0.089±0.033 ng for Z11-16:Ac, 0.085±0.031 ng for Z5-10:Ac, 0.105±0.065 ng for Z8-12:Ac per female. The percentages of Z7-12:Ac, Z9-14:Ac, Z11-16:Ac, Z5-10:Ac and Z8-12:Ac in pheromone gland extracts from individual females were (mean±SE) 40.451±13.66, 13.176±5.279, 14.943±5.142, 14.392±6.10 and 17.225±9.792 respectively, and the percentages of Z7-12:Ac, Z9-14:Ac and Z11-16:Ac were 58.75±9.429, 18.91±7.539 and 22.34±7.209. Field trials indicated that each single component of sex pheromone was non-effective and captured no males. The lures baited with duality compound of AB (3∶1) had a certain attraction to males, the mean captured number was 2.6. The attraction ability of the lures baited with ternary compound of ABC (3∶1∶1) to males added significantly, the mean captured number per trap was 7.40, which was 2.8 times of duality compound of AB (3∶1). The contents of sex pheromone could obviously affect its capture ability to males, the mean captured number was the highest at the dosage of 200 µg.