It is of great significance for optimal controlling the freeze-drying process to determine the end of sublimation drying and desorption. The drying dynamical characteristics test for Fuji apple were carried out using the JDG-0.2 type vacuum freeze-drying machine. Based on the homemade real-time online measurement system, the moisture content of apple blocks was measured, and the changing curve was drawn during the freeze-drying process. According to the measured data, the freeze-drying dynamical characteristics were analyzed, the judgment method for the end of sublimation drying and desorption was proposed. It provides the means for optimal controlling parameters during the freeze-drying process.