Abstract: America and Pakistan became allies according to their own strategic consideration，and Pakistan turned into America′s front line and nonNATO ally in America′s global war against terrorism.But Pakistan became America′s frontline country largely due to Pakistan′s special geopolitics.The USPakistan cooperation in counterterrorism is not as effective as the institution of USIndia and USEuropean Union，as there is not a longterm cooperation mechanism between the two countries.This paper analyzes the cooperation process and the effect within Bush administration，Obama administration and the postLaden Era，and makes some forecast for the future of the cooperation in antiterrorism as well.The author holds that America will pay high cost to maintain USPakistan cooperation in combating terrorism regardless of a lot of controversies between the two sides.

Key words: America, Pakistan, terrorism, cooperation in counterterrorism, AfghPak Strategy, postLaden Era 