The invention discloses a dehumidifier and a control method thereof. The dehumidifier comprises a machine shell, a semiconductor dehumidifier, a heater, a controller, a temperature and humidity sensor and an LCD display screen. The semiconductor dehumidifier is composed of a semiconductor assembly, cold fins, hot fins and a heat-radiating fan assembly. The semiconductor dehumidifier and the heater, which are fixed together, are installed in the machine shell. The controller is installed at the secondary chamber cabinet plate of target equipment. The temperature and humidity sensor is installed in a temperature and humidity chamber requiring the controller and is away from heating and dehumidifying integrated equipment. The controller is electrically connected with the temperature and humidity sensor, the semiconductor dehumidifier and the heater respectively via data lines. The temperature and humidity sensor acquires temperature and humidity data of the machine shell and transmits the temperature and humidity data to the controller via the data lines. The controller controls work of the semiconductor dehumidifier and the heater. Refrigeration and dehumidifying are performed by the semiconductor dehumidifier, and absolute humidity of the environment is reduced. After the semiconductor dehumidifier works for a period of time, humidity in the cabinet is obviously reduced. After the semiconductor dehumidifier stops working, humidity does not rise instantly so that a defect that dehumidifying equipment needs to be used after stopping working instantly can be avoided, and thus the dehumidifier has advantages of being accurate in dehumidifying and great in dehumidifying effect.