The invention discloses a device which can automatically control temperature and humidity, as well as the method thereof. The device of the invention comprises an air conditioner, a damping machine, a dehumidifying machine, a ventilation system, a constant temperature lamp, a constant humidity lamp, a display and a printer, as well as a central control system which is connected with the air conditioner, the damping machine, the dehumidifying machine, the ventilation system, the constant temperature lamp, the constant humidity lamp, the display and the printer. The method of the invention comprises the following steps: the indoor temperature and the indoor humidity which need to be controlled are determined and the maximum and the minimum of the temperature and the maximum and the minimum of the humidity are set according to the needs, and the indoor and the outdoor temperature and the indoor and the outdoor humidity are measured; whether the ventilation system, the air conditioner, the damping machine and the dehumidifying starts or set under the constant temperature or constant humidity state is judged according to the indoor temperature and the indoor humidity which need to be controlled as well as the difference between the maximum and the minimum of the temperature and the maximum and the minimum of the humidity which are set and the indoor and the outdoor temperature and the indoor and the outdoor humidity; the ventilation system, the air conditioner, the damping machine and the dehumidifying are started or set under the constant temperature or constant humidity state according to the judgment of the result.