A dehumidification mode control method, comprising: obtaining a dehumidification load of a heat pump system and an external ambient temperature when it is detected that a passenger compartment has a dehumidification demand, wherein the heat pump system comprises an external heat exchanger and a first internal heat exchanger, a second internal heat exchanger, a compressor, a first electronic expansion valve, a second electronic expansion valve and an air transmission heat exchange box; determining (S202, S303) whether to enter a first dehumidification mode according to the dehumidification load, the external ambient temperature and a load threshold, wherein the first dehumidification mode is configured to perform heat supplement and temperature elevation on air which has flowed through the first internal heat exchanger, using heat absorbed from an external environment through the external heat exchanger during a dehumidification process; if yes, determining a control instruction of the first dehumidification mode according to an air temperature at multiple first preset positions in the air transmission heat exchange box and a subcooling degree of a heat exchange medium at at least one second preset position in a transmission pipeline, wherein the first preset position comprises an air outlet of the air transmission heat exchange box and an air outlet side of the first internal heat exchanger; and outputting the control instruction so that a first target temperature and a second target temperature simultaneously meet a preset requirement of a dehumidification function, wherein the first target temperature comprises an air temperature at the air outlet, the second target temperature is an air temperature at the air outlet side; wherein, in the first dehumidification mode, the control instruction comprises a closed-loop control instruction for performing closed-loop control on each object to be controlled in the heat pump system, a function of the object to be controlled comprises circulating the heat exchange medium along a parallel circulation path in the transmission pipeline, and the parallel circulation path comprises: a heat absorption path, a refrigeration path and a heat supplement path, the heat absorption path and the refrigeration path are connected in parallel and then connected in series with the heat supplement path; the external heat exchanger is located on the heat absorption path, the first internal heat exchanger is located on the refrigeration path, the second internal heat exchanger is located on the heat supplement path, the second internal heat exchanger is configured to transfer heat absorbed by the external heat exchanger to the air which has flowed through the first internal heat exchanger. obtaining a dehumidification load of a heat pump system and an external ambient temperature when it is detected that a passenger compartment has a dehumidification demand, wherein the heat pump system comprises an external heat exchanger and a first internal heat exchanger, a second internal heat exchanger, a compressor, a first electronic expansion valve, a second electronic expansion valve and an air transmission heat exchange box; determining (S202, S303) whether to enter a first dehumidification mode according to the dehumidification load, the external ambient temperature and a load threshold, wherein the first dehumidification mode is configured to perform heat supplement and temperature elevation on air which has flowed through the first internal heat exchanger, using heat absorbed from an external environment through the external heat exchanger during a dehumidification process; if yes, determining a control instruction of the first dehumidification mode according to an air temperature at multiple first preset positions in the air transmission heat exchange box and a subcooling degree of a heat exchange medium at at least one second preset position in a transmission pipeline, wherein the first preset position comprises an air outlet of the air transmission heat exchange box and an air outlet side of the first internal heat exchanger; and outputting the control instruction so that a first target temperature and a second target temperature simultaneously meet a preset requirement of a dehumidification function, wherein the first target temperature comprises an air temperature at the air outlet, the second target temperature is an air temperature at the air outlet side; wherein, in the first dehumidification mode, the control instruction comprises a closed-loop control instruction for performing closed-loop control on each object to be controlled in the heat pump system, a function of the object to be controlled comprises circulating the heat exchange medium along a parallel circulation path in the transmission pipeline, and the parallel circulation path comprises: a heat absorption path, a refrigeration path and a heat supplement path, the heat absorption path and the refrigeration path are connected in parallel and then connected in series with the heat supplement path; the external heat exchanger is located on the heat absorption path, the first internal heat exchanger is located on the refrigeration path, the second internal heat exchanger is located on the heat supplement path, the second internal heat exchanger is configured to transfer heat absorbed by the external heat exchanger to the air which has flowed through the first internal heat exchanger.