The Korean nuclear issue is, in essence, a matter of relationship between the U.S. and North Korea,(DPRK). Since the outbreak of the Korean nuclear crisis in October 2002, the matter has been a long delay and increasingly complicated. The U.S. tough policy toward North Korea is beyond doubt the most important external element and the main cause for triggering off a new round of the Korean nuclear crisis. Therefore, reviewing and straightening out the U.S. Korean policy of the Bush administration from its very beginning, and profoundly analyzing its policy choice and the aftermath on Korean nuclear issue after the U. S. mid - term elections, will surely be helpful to the study and assessment of the Korean nuclear issue's future development.