Abstract: With the “three rules” going into effect， both issues and doubts have been introduced into criminal procedures， and they differ in the basic attributes， modes of action and main functions. Issues-formation and doubts-formation are two forms of the defenders' burden of proof， but they have long faced many misunderstandings. Issues-formation arises from the common law， which is combined with the burden of producing evidence， and has become the basic content of the burden of proof. Doubts-formation comes from the civil law and is regarded as the inevitable result of the inquisitorial system. At the normative level in China， issues-formation and doubts-formation are reflected， but there are changes in the forms of responsibility. The burden of producing evidence is diluted， and the relatively independent issues-formation has formed. The inquisitorial system is weakened， while the strong doubts-formation has emerged. The improved burdens of issues-formation and doubts-formation coexist in China's criminal procedure， in which there is a possibility of transformation. Based on the different matters， a hierarchical theory of combining both burdens comes into being.

Key words: burden of proof; defender; burden of issues-formation; burden of doubts-formation; hierarchical theory