The invention provides a heat pump drying system. The heat pump drying system comprises a drying chamber, a fan, a first evaporator, a second evaporator, a compressor, a condenser, a throttle valve, afirst outside air damper, a second outside air damper, a first air filter, a second air filter, a heat exchanger, a three-way valve, a controller and a temperature and humidity sensor. The first evaporator and the second evaporator arranged in parallel, and the first evaporator and a coiled pipe of the condenser are connected in series; the fan is arranged between the first evaporator and the second evaporator; and an air outlet of the fan directly faces an air inlet of the condenser and communicates with the air inlet of the condenser, so that large-flow dry air is supplied. A bypass pipeline is arranged on a connecting pipeline between the compressor and the condenser, the bypass pipeline enters the condenser at a predetermined distance H from an inlet point of the coiled pipe of the condenser and communicates with the coiled pipe, and a three-way valve is arranged at the intersection between the bypass pipeline and the connecting pipeline. By driving the three-way valve, the heat dissipation performance of the condenser can be changed, and the heat balance can be conveniently controlled.