Aiming to solve the problems of low efficiency, easy deterioration, high energy consumption and unfavorable conditions for high-quality storage in the drying process of medicinal herbs, it is crucial to optimize the drying method. By vacuum low-temperature evaporation drying technology, a heat pump drying system was designed with a vacuum drying chamber as the mass transfer system to conduct low-temperature drying. The system was composed of equipment such as a vacuum low-temperature drying system driven by a heat pump compressor, a vacuum pump and a variable-frequency fan. The performance of the system was studied through experiments, and the effects of heat pump condensation temperature, air inlet velocity, and air inlet temperature on the drying performance of the system were analyzed. Under experimental conditions with environmental vacuum ranging from −40 to 0 kPa, the maximum values of drying capacity, drying efficiency, mass transfer coefficient, and heat transfer coefficient for the heat pump vacuum low-temperature drying system were 3.96 kg/h, 44.19%, 3.75 g/(m2.s), and 3.25 W/(m2.℃) respectively. The maximum values of mass transfer coefficient and heat transfer coefficient in the dehumidification process were 44.51 g/(m2.s) and 36.03 W/(m2.℃) respectively. The maximum coefficient of performance (COP) for the heat pump system was 6.08. Regression analysis was conducted on the experimental data to obtain the correlation equation for the drying efficiency in the heat pump vacuum low-temperature drying system. The maximum deviation between the calculated values and experimental values was within ±21%, and the average deviation was 9.18%, indicating a good predictive performance. Compared with the heat pump low-temperature drying technology at normal pressure, the heat pump drying system based on vacuum low-temperature drying technology effectively improves the efficiency of herb drying and reduces energy consumption in the herb drying process, ensuring the high-quality storage of medicinal herbs.