Presumption, a legal relation set up between foundation facts and presumed facts, is a supplementary method to propel the proof of facts in cases. However, in order to avoid over-interpretation of presumption, which is to trigger deviance of concept and application rules, its concept and application conditions should be defined. This article hereby argues that the very nature of presumption both limits its application in only the presumption of law, excluding the inference to facts unknown by judicial magistrate, and denies the possibility of conclusive evidence or fact. The function of presumption is to shift the burden of proof, which will go against Presumption of Innocence in criminal procedure. This determines the presumption that is mainly used in the field of civil litigation, being not evidence, could not reach the standard of proof of “beyond reasonable doubt” in criminal cases.