Taking the Myrica rubra Dongkui as the raw material, made use of the home-made online measurement system to monitor the weight and temperature of red bayberry during freeze-drying process in vacuum and low temperature environment to get the changing curve. According to the online data of temperature and weight of red bayberry during freeze-drying process from our online measurement system and moisture adsorption rate of freeze-dried red bayberry can be used as an indicator for determining sublimation drying end time. In addition, the central temperature or weight variation rate of freeze-drying product can be used for estimating desorption drying end time. Under given experimental conditions in this paper, the optimized red bayberry freeze-drying process was: average temperature of the eutectic point of 20.5 ℃, average eutectic temperature of 17.7 ℃, setting temperature of separation plate at 20.0 ℃ during sublimation drying stage, 50.0 ℃ during desorption drying stage and 30.0 hours of sublimation drying time. Freeze drying red bayberry had red violet color, a form complete, a crisp and rich red bayberry taste, which was easy to store.