The invention relates to a high heat unit, and a method, system and air condition for controlling the unit. According to the invention, a condensation side inlet and an evaporation side inlet of an intermediate heat exchanger are both connected with an indoor heat exchanger. A condensation outlet of the intermediate heat exchanger is connected with an outdoor heat exchanger. The evaporation side outlet of the intermediate exchanger is connected with a gas liquid separator. A pipeline connecting the evaporation side inlet of the intermediate heat exchanger with the indoor heat exchanger is provided with a third throttling device. A second throttling device is arranged on a pipeline connecting a condensation outlet of the intermediate exchanger and the outdoor heat exchanger. According to the invention, by adopting a method of heating low-pressure side cold medium by utilizing the intermediate heat exchanger and by controlling the opening degrees of the throttling devices based on a specific logic, the integral evaporation pressure and the evaporation temperature of the system are improved, the cold medium heat energy after condensation is utilized effectively, the integral heat exchange volume of the unit is improved and the low temperature heating capability is enhanced.