Abstract: Based on the space environment of manned spacecraft, this paper analyzes the surface charging mechanism. Simulations are conducted to calculate the charging potential as the structure passes through the earth magnet field, to reveal the influence of the surface charging on astronaut extravehicular activities. Some security protecting measures are proposed for the extravehicular activities(EVA). The active potential control approach is proposed to solve the high transmitter current and provide a design guidance for the EVA safety.