Flashover on polluted insulators is the most common accident occuring in power system. A great amount of work has been done to study the flashover characteristics on various kinds of insulators with several theoretical models proposed. In these models, the amount and the distribution of the pollution on the insulator is critical to the flashover performance. However, very few simulation works has been carried out to study the pollution accumulation characteristics on the insulators. In this paper, both experimental and numerical efforts were given to study the pollution accumulation characteristics in order to evaluate the flashover probability. Experiments were performed first to have a bird view on the overall pollution distributions considering several crucial influential factors such as the wind speed and wind direction. AC porcelain insulators （XWP2-160 type） were selected as the experimental samples and the equiva lent salt deposit density （ESDD） was measured after the total predetermined amount of pollution was reached. Then, aerodynamic simulation was carried out to study the airflow and velocity distributions on each part of the insulator in clean air with regard to different wind speed and direction. It was found that the amount of the pollution on each see tion of the insulator has clear connections to the wind speed or air pressure distribution on the insulator surface. These distributions coincide to the pollution distribution obtained from experiments. Besides, the wind speed and air pressure distribution along the insulator chain was also studied. This work has shown that the numerical simulation may predict the pollution distribution on the insulators with practical accuracy. It is also possible to design new insulator shapes to reduce the pollution accumulation on critical areas according to the analysis in this work.