Abstract: To study the mechanism of tobacco cytoplasmic male sterility, high-performance liquid chromatography was used to measure the contents of endogenous hormones (ZRs, iPAs, GA, ABA and IAA) in leaves and buds of tobacco cv. K326, K394 and Yunyan 87 with male-sterile and maintainer lines, and the ratios between different endogenous hormones were also analyzed. The results showed that except for the seedling stage of Yunyan 87, the content of IAA in leaves of maintainer lines was higher than that of male-sterile lines in all the cultivars. At flower-bud appearing stage, the ABA content in buds of maintainer lines of K326, K394 and Yunyan 87 were 2.2, 5.2 and 2.6 times that of male-sterile lines, respectively. The contents of ZRs in leaves of male-sterile lines increased first then decreased in all the cultivars. In leaves of Yunyan 87, the content of GA in male-sterile lines was significantly lower than that in maintainer lines. At flower-bud appearing stage, the ratios of IAA/ABA and GA/ABA in buds of male-sterile lines were higher than those in maintainer lines; the ratio of (ZRs + iPAs)/ABA in leaves of male-sterile of K326 was 33.9 times that of maintainer lines. At flowering stage, the ratio of GA/iPAs in buds of male-sterile lines of K326 and K394 was higher than that in maintainer lines, while it was contrary in leaves. For all the cultivars, the ratio of (ZRs+iPAs)/GA in leaves of male-sterile lines was higher than that in maintainer lines at flower-bud appearing stage, while it was contrary at flowering stage.