Abstract: Objective Explore the affecting factors of mentally prisoner′s competency to serve a sentence(CSS), establish the base of quantitive study of CSS. Methods Firstly, the researchers compile a questionnaire named legal-psycho ability of competency to serve a sentence questionnaire, then the researchers scaling the object with RTHD, and ask all object complete the questionnaire. there a hypothesis, that the object who are cured in cured ward is incompetent to serve a sentence(ISS), and the other who are stay in rehabilitated ward is competent to serve a sentence(CSS). Results There are 185 object admitted the study, the ISS group the CSS group have significance between psychiatric and legal aspects. Conclusion At the influence of psychiatric symptoms, the mentally prisoner′s competency to serve a sentence had been impaired, and they should been transferred from prison to hospital.

Key words: competency to serve a sentence, mentally prisoner, affecting factors