The invention discloses a surface charge measuring system with an external motion control mechanism and a measuring method. The surface charge measuring system and the measuring method aim to solve the problem that under a high-voltage SF6 environment, the surface charge of a component such as an insulator in a complex shape is difficult to measure. The surface charge measuring system mainly comprises a main shell, a side shell, an upper parallel-plate electrode, a lower parallel-plate electrode, an electrostatic measuring probe and a high-speed high-voltage electrostatic potential meter. According to a surface charge measuring device provided in the surface charge measuring system and the measurement method, the operation that one of the electrostatic measuring probe and the insulator rotates and the other one of the electrostatic measuring probe and the insulator moves horizontally can be achieved simultaneously by using equipment such as a multifunctional motion controller and a stepping motor, and it is ensured that the electrostatic measuring probe can scan and measure all parts of the surface of the insulator to be measured step by step.