Objective: In recent years, the number of juvenile crime has decreased year over year; however, juvenile sex crimes have continued to increase. There is no large-scale study of juvenile sexual crime in Taiwan. In the study, the data of juvenile sexual crimes in Taiwan were to explore the psychosocial factors. Methods: This study is retrospective, and case series report approach is also adopted. Result: Eight transferred for assessment sex offenders under the age of 18 years old were used as the study subjects. Most cases had serious family problems, including unstable family structure and parents with domestic violence. All of the cases demonstrated lower intelligence or poor academic performance. Many of them had serious behavioral problems, such as, violating school rules and having substance abuse. Conclusions: there is a significant relationship between juvenile sex crimes and family problems or lower intelligence. Both may affect the growth of them in the process of personality development, stress coping, social skills and decision making, thus increasing the issue of behavior problems, substance abuse and sex crimes.