To research the influence factors of each parameter in the Weibull distribution function, with lily at different infrared radiation heater’s temperature, different pressure of drying chamber and different thickness of materials being taken as subjects, Weibull distribution function was used to simulate and analyze the dynamic curve of lily. The results showed that Weibull distribution function could simulate the vacuum far-infrared drying process well (R²=0.995 3～0.999 7 ); the size parameter α of the model was significantly correlated with the infrared radiation heater’s temperature (P＜0.01). The scale parameter β of the model was related to the pressure of the drying chamber and the materials’ thickness, while temperature did not have significant influence on it; the diffusion coefficient of moisture during drying process ranges was between 0.401 3×10^-9～1.307 5×10^-9 m²/s and the activation energy of lily during vacuum far-infrared drying process was calculated, equal to 55.130 3 kJ/mol, less than the hot air drying 86.911 2 kJ/mol. Reducing the pressure of the drying chamber does good to keeping the content of the total phenol; both the infrared lily can keep good color in radiation heater’s temperature of 140 ℃ and the pressure of the drying chamber of 12 kPa.