Abstract: The undertaking of private prosecution is a public prosecution legal system that when the victim has already raised prosecution and private prosecution is started, during which the victim loses his capacity with no legal representatives or near relatives substitution of him for the prosecution, thus public prosecution organ exercises the prosecution rights in stead of the victim. It must depend on the unification of composing factors of the private prosecution system when researching on the nature of undertaking of private prosecution. Those factors include illegality of criminal offence, infringement of personal rights and the ability of victim to prosecute by himself. After the undertaking of private prosecution, the procuratorial organ does not assume the responsibility of investigation which may be exercised by the third party or public security organ. Furthermore, counterclaim after the undertaking of private prosecution will be inadmissible