Abstract: Since the emergence of Gettier problems， modern epistemologists have focused on the element of justification， which is controversial and inconclusive in terms of its structure and function. Departing from the debates on justification， Bayesian epistemology makes an attempt to formulate a theory that is concise， straight， precise and elegant. Subjective probability is a presupposition and an appropriate entry point of understanding Bayesian epistemology. Dutch Book Argument and conditionalization serve as the two cornerstones of Bayesian epistemology. However， Bayesian epistemology has its own shortcomings， which inevitably undergoes a lot of criticism.

Key words: degree of belief, Bayesian theory, subjective probability, Dutch Book Argument, conditionalization