Abstract: By using Cinnamomum bodinieri, C. camphora and C. caudiferum as experimental materials, dynamic variations in soluble sugar, proline, soluble protein and the leakage rate of electrolyte were investigated in the process of natural cooling from October 2009 to April 2010, and their comparison was analyzed to identify the cold resistance of three camphor tree species. The results indicated that in the process of natural cooling, before the middle of December, with a shorter duration of low temperature, the leakage rate of electrolyte changed with temperature but the change was not significant. In January, the content of osmotic adjustment substance increased rapidly with four successive days of low temperature at -8 ℃. Compared with December 28, 2009, the content of soluble protein and soluble sugar increased by 16.59%, 43.44%, 24.29 % and 8.19%, 21.27%, 16.72 % on 9 January, 2010, and the increase amplitude of C. bodinieri and C. caudiferum reached a significant level. As temperatures continued to decrease, the content of osmotic adjustment substance decreased and the leakage rate of electrolyte increased; from February to March, as the temperature increased, soluble protein and proline content increased again, but the leakage rate of electrolyte reduced to the minimum, which indicated that the damage of cell membrane caused by low temperature gradually restored; a fuzzy mathematics method showed that the cold resistance of the camphor trees first increased and then reduced, but finally further strengthened. The cold tolerance abilities are ranked in the following order: C. bodinieri>C. camphora >C. caudiferum.