Repellency effects petroleum ether, ethyl acetate and n-butanol soluble extracts of Ajuga nipponensis Makino (Lamiales: Lamiaceae) against citrus red mite, Panonychus citri (McGregor) (Acari: Tetranychidae), adult females were studied. When 0.1 g·l-1 extracts were applied to mandarin (Citrus reticulata Blanco Sapindales: Rutaceae) leaves, oviposition repellency rates of the petroleum ether extracts on the leaf surfaces were 84.86%and 69.88% one and two days after treatment respectively, and those of ethyl acetate extracts were, 89.49%and 82.19% respectively for the same intervals. At the same concentration, and for the same intervals, the female repellency rates of petroleum ether extract were 85.08%and 68.88%, while those for the ethyl acetate extracts were 50.96% and 69.84% respectively. GC-MS, IR, NMR and MS were used to identify and analyze one fraction (fractionⅠ) and three compounds that were isolated from the ethyl acetate extract. FractionⅠ, which comprised long chain fatty acids, had better bioactivity than the other fractions. At 1000 μg/ml and 2000 μg/ml oviposition repellency rates on treated mandarin leaf surfaces were 74.77% and 80.77%, and, 72.59% and 73.81%, respectively, 1 d and 2 d after mites were placed on treated leaves. At 2000 μg/ml, the female repellency rates were 69.88%and 74.24%, respectively, 1 d and 2 d after treatment. The three compounds were identified as acacetinⅡ, ajugacumbin B Ⅲ and 20-hydroxyecdysoneⅣ. None of these compounds had any repellency effect on citrus red mite females when they applied 2000 μg/ml to mandarin leaves. Repellency effects of four identified compounds in fractionⅠ, hexadecanoic acid, hexadecanoic acid methyl ester, hexadecanoic acid ethyl ester and octadecanoic acid methyl ester, were also studied. All of these compounds were active against citrus red mite females when applied to mandarin leaves at 2000 μg/ml: oviposition repellency rates were 75.18%, 61.76%, 59.18%, and 66.49% respectively, one day after treatment, and 66.67%, 31.15%, 46.75%, and 44.84% respectively, two days after treatment. At the same concentration, female repellency rates for these chemicals were 67.53%, 63.79%, 59.26% and 68.00% respectively, one day after treatment, and 67.23%, 43.96%, 48.23%, 64.19%, respectively, two days after treatment. For 1000 μg/ml 1 d after treatment, oviposition repellency rates were 59.21%, 59.16%, 57.02%, 61.40% respectively for the four chemicals, and the female feeding repellency rates were 69.64%, 61.43%, 55.76%, 64.00% respectively.