Four-rotor aircraft is a multi-rotor aircraft, which belongs to non-axis dish-rotor aircraft in rotor layout, and its four rotors are symmetrically distributed in a cross shape. Compared with traditional single-rotor aircraft, quadrotor aircraft has many advantages. The four rotors of a quadrotor aircraft cancel each other's rotation effects, and the tail rotor of a single-rotor aircraft is not needed, which is more energy-saving and reduces the size of the aircraft. Four-rotor aircraft can adjust the attitude of the aircraft by adjusting the rotation speed of four rotors. Without the propeller inclination adjustment device of single-rotor helicopter, the mechanical design is simpler: the load of four-rotor helicopter is larger, and the blades can be made smaller, which is easy to be miniaturized. Because quadrotor aircraft has so many advantages, it has a wide application prospect and research value.