Abstract: For a long time, the academy always thinks witness is a litigant except parties, who has known the facts of case and should testify at court. So witness is the natural person that cannot be substituted and does not have a connection with the case. This is right. However, what are the facts of case? Whether do they have the standard of time? Whether can witness be challenged? How to define the competence of witness? Can the policeman appear in court as a witness? The circles of justice and academy always do not attach importance to these problems, and have much a mbiguous knowledge about witness. Therefore, witness in criminal procedure is the concept that should be immediately re-molded both in legislation and theory.