The standardized management level of prisons is gradually improving, and the form of supervision and security is stable. However, there are still many inmates who do not confess and repent, and even commit repeat crimes inside the prison. Among them, premeditated crimes have a long preparation period and strong concealment, often difficult to detect, and once they occur, the consequences are very serious. There are still limitations in the investigation and prevention of premeditated cases in prison, such as poor results in the rehabilitation of a small number of criminals’ bad habits, limited sources of clues, weak investigation techniques, and inadequate departmental cooperation mechanisms. Based on the above issues, it is proposed to use psychological testing techniques to intervene in a timely manner after discovering criminal clues, assist in discovering the tools and hidden locations of the crime, analyze the number of criminals, the motive for the crime, and the remaining crimes and omissions, in order to further strengthen the foundation of regulatory safety and improve the quality of criminal rehabilitation.