Abstract Gas-insulated systems are now a major component of power transmission and distribution systems all over the world. There has been considerable interest in non-thermal discharges over the past decade due to the increased number of industrial applications. Diverse applications demand a solid physical and chemical understanding of the operational principals of such discharges. This paper focuses on the most important and widely used variety of non-thermal discharges, the corona discharge. Positive corona in SF6 is studied for a point to plane electrode gap using Monte Carlo simulation technique. The initiation and development of successive avalanches are traced as function of time. The simulation provides a detailed structure of avalanches from which essential properties of corona discharge with regard to total field distribution, propagation of successive avalanches and ion distribution can be discerned.