Abstract: Insulating stick is an important safety tool for live working in the maintenance of distribution network system. The insulation performance of the insulating stick will decrease obviously under the condition of wet, defects and pollution. Therefore, an effective and reliable method to evaluate the insulation performance is proposed by studying the influence of the surface state of the insulating stick on the flashover voltage along the stick surface.Which is very important to ensure the safety of maintenance personnel and equipment. IDAX-300 was used to detect the dielectric loss factor of insulating stick. The insulated stick samples wrap around copper foil paper at a distance of 2cm between the two sides were tested to attain the surface flashover voltage in a closed environment. The oscilloscope was used to record the flashover voltage waveform during the flashover along the stick surface, and Xviewer software was used to analysis the data after the tests. The results show that the insulation performance of the insulating stick will decrease with the process of pressurization due to the gradual drying of filth under the same closed condition. When the defect is not completely distributed between two test electrodes, the defect has little effect on the insulation performance at different positions between two electrodes.