Abstract: Nowadays, many wind turbine blades are hit by lightning. But it is still unclear for the mechanism of gas burst damage caused by lightning arc and hard to measure relevant parameters during the damage process through traditional experimental methods. Hence, this paper establishes a lightning arc geometry model with reference to real blades. Based on magneto hydrodynamics theory, finite element simulation software COMSOL was used to investigate the distribution of temperature and pressure inside the blade. Furthermore, we analyzed the influence of different arc ignited methods and lightning strike positions on the carbonization degree of blade materials and the maximum pressure at the trailing edge. It is found that after suffering lightning strike, the temperature at lighting strike point increases steeply to maximum, then decreases slowly, and the high temperature area mainly distributes around the arc path. The pressure at the trailing edge first rises to the peak value and then shows a trend of turbulent decrease. High pressure area first distributes between the right web and trailing edge and then gradually spreads into whole blade cavity. Blade carbonization degree and the maximum pressure at trailing edge match the experimental results of previous literatures, which verify the correctness of simulation model. When lightning strike point is closer to the tip of blade, blade’s carbonization degree is more severe and so is the trailing edge’s maximum pressure. When the down-conductor is set on the main beam, the above two parameters are smaller than that when set on the right web. Finally, from the perspective of lightning protection, the authors suggest setting the down-conductor on the main beam, meanwhile using epoxy resin to cast the trailing edge into a rounded corner with the radius of 30 mm.