The utility model discloses a forest fire hazard early warning system based on an unmanned helicopter, belonging to the field of forest fireproof. The system comprises an unmanned helicopter and a ground station. The unmanned helicopter comprises a casing, a rotor arranged on the casing, a power apparatus and a control unit arranged in the casing, a pair of undercarriages arranged below the casing, a bracket arranged between the pair of the undercarriages and a flame detector, a temperature sensor and a humidity sensor arranged on the bracket. A thermal reflection material layer covers a surface of the casing. The control unit comprises a first processor, a three-route data acquisition circuit, a first wireless transmission unit and a GPS positioning unit. The first processor is connected electrically with output terminals of the flame detector, the temperature sensor and the humidity sensor through the three-route data acquisition circuit. The ground station comprises an alarm unit, a second wireless transmission unit, a meteorology querying unit and a second processor. The second wireless transmission unit and the first wireless transmission unit are in a wireless connection.