The ground spoiler auto-extension logic of 7 types of civil aircraft are researched in this article,including the influences of ground spoiler armed,full/partial extension,main landing gear seen on ground and thrust levers position. At last,the influence on flight safety by auto-extension logic of ground spoiler is studied based on the example of A320 runway excursions and bounces at landing. It is concluded that the modified auto-extension logic of ground spoiler can increase the flight operation tolerance and decrease the probability of flight accidents caused by human factor.