Direct causes of the government shutdown at the federal level in the United States are the budget deficit and legislation on debt limit. There are，however，three root-causes：economic slowdown which has resulted in a slower increase in fiscal revenue and persistent increase in fiscal expenditures；the hard“budget constraint”that has been long existed in the United States in the form of legislation on debt limit for the federal government；and intensified dispute between the Republic and Democratic. Like in the time when Bill Clinton was in office，Barack Obama has been facing a hostile Congress led by the Republic，who has been mostly provocative on budget-related issues. The government shutdowns occurred only briefly，and their impacts on the life of ordinary Americans were minimal in general. Yet the impacts on international affairs and the image of the U.S. are thought be significant and considerable. First，the White House’ agenda on certain foreign affairs had to make some harsh reschedule during the shutdown period. Second，new doubt on the soundness and reliability of the working in the U.S. federal system has emerged. Third，the president’s fiscal and economic policy measures，including his Medicare，have to make change. Fourth，the total expenditure plan，including that on defense，has to be cut more or less. Fifth，the high reputation that has been long enjoyed by the United States in the world financial market has suffered a dint.