Based on the unsteady diffusion processing of ultrasonic assisted extraction of chemical composition from Chinese herbal medicine, the extraction process model of ultrasonic assisted cellulase was estibulished to extract polysaccharide from the fruiting bodies of Phellinus igniarius according to Fick's second law. The dynamics processing model of hot water extraction and ultrasonic assisted cellulase extraction was developed and verified by experiments. A series of dynamic parameters of rate constant, activation energy and relative extraction rate were analyzed. The results showed that the experimental data well coincide with the dynamic model calculated values, and the models could describe the process well. The result provided certain basis for Phellinus igniarius polysaccharide extraction magnification engineering and in-depth theoretical study of polysaccharide extraction processing.