Abstract: Electric eonductivities of excised-leaves of 7 species of Ilex trees distributed in China were measured and lethal temperature 50 (LT50) were calculated under the simulated freezing treatment. The results indicated that the low temperature tolerance ability of 7 species of Ilex trees had a significant difference, and the freezing resistance from strong to weak was Ilex latifolia, I. comuta, I. chinensis, I. rotunda, I. zhejiangensis, I. hylonoma, I. integra. Four trees selected from 7 species of Ilex trees that treated by 4℃ and -16℃ were chosen to measure the contents of unsaturated fatty acids. The results revealed the content of unsaturated fatty acids and IUFA increased as the temperature decreased, and the increasing extent of IUFA was were different respectively so they could be used as supplementary validation of the low temperature tolerance ability of different Ilex trees. The research resuits also provide important indexes for introducing Ilex trees to higher latitude region.