The paper analyses the historical background and contents of the theories of Anglo-Saxon and melting pot and effects of multiculturalism. It is pointed out that American multiculturalism underwent the transition from dominant culture to multi-culture. American multiculturalism originated from the change of the structure of ethnic groups and civil rights movement and it is reflected by pluralism of administration system, religion and education reform. American multiculturalism exerts some influences on American diplomatic policies and their life styles.