Criminal case file is an indispensable carrier in criminal proceedings, which is usually divided into internal volume and external volume. The inner volume is mainly the materials formed by the public, procuratorial and legal organs in their work and stored in their own units without being transferred to the next procedure. External papers must be transferred to the next procedure and finally used as evidence in court. In the current judicial practice, a criminal case has at least two external volumes, one is the evidence volume and the other is the document volume (technical appraisal materials are bound together with the same volume). These two volumes cannot be disassembled during the prosecution and trial stages. In the course of litigation, the whole volume is handed over. During the court hearing, the prosecutor presented the evidence with the file. After the trial, all the files were handed over to the court, and finally the court kept them as they were.