Abstract: In order to clarify the stability of cembratrien-diols (CBT-doils) and their antifungal activities, the effects of light sources, temperature, pH, and organic solvents on concentrations of CBT-doils were analyzed by ultra-performance liquid chromatography, and the antifungal effect against Phytophthora parasitica var. nicotianae was tested using the growth-rate method. The results showed that all the tested factors had significant effects on the stability of CBT-doils and the effects became more profound with exposed time. And the reduction in CBT-doils concentration was more significant than that in antifungal activity. When exposed to sunlight for 63 h, the concentration of CBT-doils decreased by (36.65±0.86)%, while the antifungal rate was reduced by (20.98±0.16)%. The stability of CBT-doils had no significant difference among various intensities of fluorescent (4-10 kLux). The concentration of CBT-doils was decreased in a temperature-dependent manner. The reduction rate was (89.03±2.29)% for the CBT-doils concentration, while (55.00±0.72)% for the antifungal activity at 80℃ for 40 h. In the pH range of 7 to 9, CBT-doils had higher stability and antifungal activity. In addition, the CBT-doils in ethanol and n-butanol were more stable than those in dimethyl sulfoxide, cyclohexanone, and n-propanol. Under different exposure conditions, β-CBT-doils were more stable than α-CBT-doils.