The criminal procedure law does not stipulate the minimum period of criminal detention. In judicial practice, generally speaking, criminal detention is at least three days. If it is a relatively simple case, the public security organ will release the suspect if it finds that the suspect does not constitute a crime within three days. It should be noted that although there is no minimum period of criminal detention, there is a statutory maximum period of criminal detention. According to the provisions of the Criminal Procedure Law, the term of criminal detention is equal to the sum of the time when the public security organ applies for approval of arrest and the time when the procuratorial organ reviews approval of arrest.
 In other words, the maximum duration of criminal detention is the maximum of the sum of the two. The time limit for the public security organ to apply for approval of arrest shall not exceed 30 days; The time limit for the procuratorial organ to examine and approve arrest shall not exceed seven days.
 [Legal Basis]
 In Article 82 of the Criminal Procedure Law of the People's Republic of China, the public security organ may first detain an active criminal or a major suspect under any of the following circumstances:
 （1） Is preparing to commit a crime, is committing a crime, or is discovered immediately after committing a crime;
 （2） The victim or the person who saw it with his own eyes on the spot identified him as a criminal;
 （3） Finding evidence of a crime on one's side or at one's residence;
 （4） Attempting to commit suicide, escape or being a fugitive after committing a crime;
 （5） It is possible to destroy or forge evidence or collude with others;
 （6） Failing to tell the true name and address, and the identity is unknown;
 （7） There is a serious suspicion of committing crimes from place to place, repeatedly, or in a gang.