An evaporative cooling unit, comprising an outdoor channel, an indoor channel, and a heat exchange apparatus, wherein the heat exchange apparatus is configured to exchange heat of air in the outdoor channel with that of air in the indoor channel; the evaporative cooling unit further comprises an air filter and a defrosting apparatus that are disposed in the outdoor channel, wherein the air filter is located between an air intake vent of the outdoor channel and the heat exchange apparatus, and the defrosting apparatus is located on a side of the air filter close to the air intake vent of the outdoor channel; characterized in that the defrosting apparatus comprises a heat exchange film, and the heat exchange film is a wet film and has a first channel and a second channel that are arranged crosswise, wherein the first channel communicates with the air intake vent of the outdoor channel, the second channel communicates with the indoor channel, and the first channel communicates with the second channel; and the defrosting apparatus further comprises a switch valve, wherein the switch valve is configured to control the second channel to communicate with the indoor channel, and in that the evaporative cooling unit further comprising a humidifying apparatus, wherein the humidifying apparatus and the defrosting apparatus share the heat exchange film; the humidifying apparatus further comprises a water supply apparatus, wherein the water supply apparatus comprises a water collection tank and a water supply component; the water collection tank communicates with one end of the second channel, and is configured to collect water flowing out of the second channel; and the water supply component comprises a water supply pipe enabling the water collection tank to communicate with the other end of the second channel, and a water pump disposed on the water supply pipe, wherein the water pump is configured to pump water in the water collection tank into the second channel. the evaporative cooling unit further comprises an air filter and a defrosting apparatus that are disposed in the outdoor channel, wherein the air filter is located between an air intake vent of the outdoor channel and the heat exchange apparatus, and the defrosting apparatus is located on a side of the air filter close to the air intake vent of the outdoor channel; characterized in that the defrosting apparatus comprises a heat exchange film, and the heat exchange film is a wet film and has a first channel and a second channel that are arranged crosswise, wherein the first channel communicates with the air intake vent of the outdoor channel, the second channel communicates with the indoor channel, and the first channel communicates with the second channel; and the defrosting apparatus further comprises a switch valve, wherein the switch valve is configured to control the second channel to communicate with the indoor channel, and in that the evaporative cooling unit further comprising a humidifying apparatus, wherein the humidifying apparatus and the defrosting apparatus share the heat exchange film; the humidifying apparatus further comprises a water supply apparatus, wherein the water supply apparatus comprises a water collection tank and a water supply component; the water collection tank communicates with one end of the second channel, and is configured to collect water flowing out of the second channel; and the water supply component comprises a water supply pipe enabling the water collection tank to communicate with the other end of the second channel, and a water pump disposed on the water supply pipe, wherein the water pump is configured to pump water in the water collection tank into the second channel.