Few studies have examined the relationship between criminal intention and practice. However, investigations in this field have implications in crime prevention. Sexual aggression against children causes severe harm to victims, has a prevalence, and is associated with major social concerns; therefore, the present study investigated the relationship between child sexual aggression intention and practice and its impact factors. An anonymous self-report questionnaire was adopted to collect data from 915 incarcerated males at Taipei, Taichung, and Kaohsiung prisons in Taiwan and 559 male college students from 6public and private universities in Taipei and Hsinchu. The results show that the intention and practice of child sexual aggression are related. Child sexual aggression intention accounts for 13.7~28.0%, 2.2~8.4% variances of practice separately in male inmates and college students. Besides, deviant sexual arousal (pedophilia tendency), cognitive distortion (child sexual aggression myth acceptance), antisocial personality disorder tendency, and viewing child pornography are factors influencing the relevance of child sexual aggression intention and practice among male inmates. Antisocial personality disorder tendency, cognitive distortion, and viewing child pornography are factors influencing the relevance of child sexual aggression intention and practice among male college students. The impact factors and the amount of variance they can account for the relevance of child sexual aggression intention and practice are different in the two samples. Finally, this paper discusses the implications of the research results, practical applications, limitations, and directions for future research.