As a common type of discharge in GIS, surface discharge is still unclear in its microscopic process, and there is also a lack of theoretical correlation between partial discharge and signal detection. Based on the fluid-chemical simulation model, the surface discharge process in SF6 was simulated, and the variation laws of charged particle concentration and surface streamer velocity were obtained. Using the current pulse calculated in the microscopic simulation as an excitation, the discharge signals generated by the surface discharge was simulated based on the finite integral method, and the relationship between the microscopic process of the partial discharge and the discharge detection signal was established. Compared with the signal excited by the traditional Gaussian source, the electromagnetic signal time-domain waveforms obtained by the micro-discharge simulation are more realistic. The research results are an effective supplement to the existing research on the microscopic mechanism of partial discharge signals, laying the foundation for the insulation state evaluation based on the analysis of discharge signals.