In the process of the development of economic thought,corporate profit is a crucial topic discussed by economists.Frank Hyneman Knight,a famous American economist,as the founder of the Chicago School,emphasizes the distinction between risk and uncertainty and proposes his unique views on the relationship between risk,uncertainty and profit from a new perspective.This paper deeply reviews Knight's views on uncertainty and firm profit in his book,Risk,Uncertainty and Profi t,and compares the classic uncertainty theory and firm theory in the history of economic thought.This article affirms Knight's creative contribution to the study of firm profit,and makes comments on Knight's opinions at last.