“Personal dangerousness” is a newly-developing concept with the rise of criminal positivism school. At present, there are two kinds of different definitions of the “personal dangerousness” in the field of criminal jurisprudence. In a narrow sense, it refers to the possibility that an offender commits a crime again(Qu Xinjiu, 2000). Broadly speaking, personal dangerousness is the combination of the possibility of the first offence and the possibility of the second offence (Chen Xingliang, 2004). As the researchers’ angles of view are different, the concept of personal dangerousness varies. In this research, the “personal dangerousness” is defined as the possibility that the criminals serving sentences seriously violate the prison regulations, commit crimes in jail and recommit crimes after release ( Huang Xingrui, 2004). Criminals with high personal dangerousness, not only have the possibility of committing a crime again, but also infect others as a source of crime (Zhao Linhu, 2010). Therefore, it is necessary to study the key factors and mechanism of the personal dangerousness. This study aims to explore the mediated moderation among personality, social support, mature coping style, and personal dangerousness after controlling several variables which conclude age, education, marital status, and crime times. 463 male criminals from four prisons in Zhejiang Province took part in the questionnaire survey. The self-report questionnaires included Eysenck Personality Questionnaire, Social Support Rating Scale, Mature Coping Style Questionnaire and Criminal Personal dangerousness Checklist Scale. The data were analyzed by the Structural Equation Model using the AMOS 5.0 program. The results were that the mediated moderation model provided a good fit to the data, X2 = 93.75, df = 27, p < .001, NFI = .95, IFI = .96, CFI = .96, RMSEA = .073. Our findings are as follows: (1)Risk factors, which affect criminals’ personal dangerousness, are age, education level, marital status and crime frequency. In other words, the younger the male criminal, the higher his personal dangerousness; the more frequently the criminal commit crimes, the lower the possibility he regrets and accepts the education correction and the higher his personal dangerousness; the lower his education level, the more difficult for him to accept correction, and his personal dangerousness will be higher; the unmarried and divorced, because of lack of family limitation and low sense of social responsibility, have higher personal dangerousness. (2)Personality of male criminals affects personal dangerousness greatly as personality and personal dangerousness are significantly positively correlated. Male criminals, who are extroverted, tend to be more dangerous and have higher possibility to commit crimes again after rehabilitation. (3)social support moderates the effect of personality on personal dangerousness, so we should focus on improving the level of their social support, from which they may experience warmth and power of kinship, to strengthen the “reducer” effect of social support. (4)mature coping style mediates this moderation effect. Therefore, courses about the coping ability of male criminals can be set to cultivate their ability of thinking positively when faced with difficulty and stress. Psychological intervention schemes can also be developed to cultivate mature coping skills to lower the personal dangerousness of male criminals by intervening this mediating variable. In conclusion, the results of the above study stress the influence of male criminals’ social support and mature coping style on lowering personal dangerousness, which are meaningful for prison work.