The invention discloses a ventilation and air-exchange device for an internet-of-things intelligent greenhouse. The device comprises a temperature sensor, a humidity sensor, a controller, a ventilation assembly and an air-exchange assembly. The temperature sensor and the humidity sensor are arranged inside the internet-of-things intelligent greenhouse. The controller is arranged outside the internet-of-things intelligent greenhouse. The temperature sensor and the humidity sensor are used for sending detected temperature and humidity signals to the controller. The controller controls the ventilation assembly and the air-exchange assembly to run. The ventilation assembly comprises an air-induced port, an air-induced port sealing cover, an air inducing device, an air inlet main pipeline, an air inlet branch pipeline, an air outlet and an air outlet sealing cover. The air-exchange assembly comprises an air-exchange main pipeline, an air-exchange branch pipeline and an air heating device. Afirst switch valve is arranged on the air inlet main pipeline, and a second switch valve is arranged on the air-exchange main pipeline. The first switch valve and the second switch valve are connected with the controller. The device is switched between the ventilation mode and the air-exchange mode according to the temperature and humidity conditions.