【Objective】To explore the relationship between CO₂ filling amount and the performances of the heat pump dryer system including the system power, the drying chamber temperature and the system performance coefficient, and to determine the optimal CO₂ filling amount.【Method】The working principles of the heat pump dryer were analyzed according to the actual production requirements. The CO₂ heat pump drying experimental platform was established. Data collection and monitoring system design were conducted by PLC. CO₂ filling experiments were performed.【Result】When the CO₂ filling amount was 2.5 kg, the system power reached 1 200 W, the drying chamber temperature reached 70 ℃, the energy consumption rate （C_OP） was 3.89, the dehumidification rate was 1.636 kg·h^-1, the pressures of the cooler and evaporator were suitable, and the temperature difference between inlet and outlet was relatively large.【Conclusion】This system has high energy efficiency and excellent performance.