Abstract: At the 1787 constitutional convention,the founding fathers of the United States designed the Electoral College system.However,this system had some inherent defects,leading to electoral crisis in 1800.The Twelfth Amendment of the Constitution came into existence to avoid the recurrence of the crisis.After more than 200 years,the Electoral College system has changed profoundly,and conflicts have appeared between stipulation of the constitution and the electoral reality.Though it is appealed to abolish this system,so far the Congress has not made a second revision of the system due to various factors.

Key words: US.President, the Electoral College system, the Twelfth Amendment of the Constitution