This research uses “possibility satisfiability” method to calculate the appropriate urban population carrying capacity of Beijing in different possible satisfaction conditions. The results of the study show that，the control core factor to promote the Beijing urban population carrying capacity is the ability of the urban infrastructure construction such as traffic，garbage disposal. Although water resources restricted the Beijing urban population carrying capacity as the important short board，but through the cross regional water transfer and stronger the intensive use of water resources，Beijing can better solve the problem of water shortage.