Abstract: In recent years, forest fires have areoccured frequently caused by electrical faults all over the world, which seriously threaten people's life and property safety. Aiming at the accidents of vegetation ignition caused by the tree- contacting sin-gle-phase-to-ground faults of the overhead lines, a tree-line contacting simulation test platform was established, and the ignition mechanism of vegetation under a high voltage electric field was analyzed based on the typical characteristics of vegetation ignition process in the test. The Rresults surfaceindicate: 1) The process of discharge ignition can be divided into four typical stages corresponding to the changeing characteristics of electricalcurrent leakage characteristics; 2) CumulativeThe continuous current conduction time and the initial current are the keys to determine whether the ignition canmay occur and how it develops; 3) The arcs inat the contacting areapoint and in the carbonization channel canmay promote the development of flames and further reduce the insulation ability of the vegetation; 4) There is a game between the "carbonization effect" and the "cooking effect" happening in the ignition process, which leadsing to the change of electrical signals in time domain; 5) The carbonization channels arepresent the typical shape of electrical dendritice, and thewhose conductive channels in the dendrites are concentrated aton the interfaces between the epidermis and the trunk. According to the test and analysis, the vegetation ignition under a high voltage field has the characteristic of stage development. Accurately extracting and identifying the characteristics of vegetation combustion in different each stages of vegetation combustion will be helpful to improve the technology of fault detection technology.