The invention discloses a rotor wing flight mechanical arm system and algorithm based on dynamic gravity center compensation. The system comprises a rotor wing flight platform, an image sensor, a connecting frame, a mechanical arm system, a system controller and a ground station control device. The rotor wing flight platform comprises a rotor wing aircraft and a flight controller. The image sensoris installed below the front part of the rotor wing flight platform. The connecting frame is a mechanical plate which is used for fixedly connecting the rotor wing flight platform, the image sensor and the mechanical arm system. The mechanical arm system is installed just below the rotor wing flight platform. The system controller is installed right above the rotor wing flight platform. The ground station control device is communicated with the system controller in a wireless mode. The system is rational in structural design, high in safety, and strong in stability. The algorithm is capable of improving the accuracy rate of capturing, and improving the time efficiency of capturing.