American independence is the very significant event in the history of British Empire development.According to this milestone,British Empire’s history can be divided into the first British Empire and the second British Empire.This essay elaborates on the first British Empire and the reason of its collapsing.It also probes into the internal motivation,adopted governing policy and development process of the second British Empire,which was based on the collapse of the first British Empire.Among them,American Independence was the historic opportunity which facilitated British government’s reflection and total transformation on old colonial theory.