The invention discloses a VFTO test system and a VFTO test method of composite insulator surface pulse ratio. Each ultraviolet lamp is turned on through a console to simulate an intensive ultravioletarea; after radiation for a period of time, a control platform is triggered to generate a VFTO signal acting on an insulator, the control platform controls a high-voltage direct current power supply to work, detects leakage current and uploads and processes data. The test system and the test method can simulate working conditions of running under the intensive ultraviolet area of a composite insulator, generate the VFTO signal through simulation, realize test on influence of intensive ultraviolet radiation VFTO on surface performance of the composite insulator. In the method and the system, afirst capacitor, a second capacitor and a third capacitor form multi-stage capacitors to jointly perform charging and discharging, and in combination with pulse steepening clearance, amplitude of waveform and waveform stability are improved, simultaneously, a wave modulation module is added for compensating waveform distortion, thus, defects, such as insufficient voltage level, relatively high loop inductance and serious waveform distortion, in the existing system are overcome.