The invention relates to an insulating material surface charge measuring system and method. The insulating material surface charge measuring system comprises a light source generator, a polarizer, a phase modulator, an electro-optic crystal, a high-voltage electrode and a photosensitive unit, wherein the polarizer, the phase modulator, the electro-optic crystal and the high-voltage electrode are arranged sequentially along an optical path of emitted light of the light source generator; the high-voltage electrode and the electro-optic crystal are arranged at an interval; the photosensitive unit is sued for receiving reflected light passing the polarizer and recording light wave intensity of the reflected light. According to the insulating material surface charge measuring system, a to-be-measured insulating material is arranged in the interval between the high-voltage electrode and the electro-optic crystal. The high-voltage electrode applies high voltage to the to-be-measured insulating material, and charged particles are enabled to be accumulated on the surface of the to-be-measured insulating material to form an electric field. A worker records the light wave intensity of the reflected light by aid of the photosensitive unit, and further, phase difference, electric field intensity as well as surface charge distribution of the insulating material are obtained sequentially through calculation.