The complexity and diversity of child molestation behavior itself have long troubled the theoretical and practical circles with the standard of conviction of this behavior. The key to determining the standard of conviction lies in judging the degree of illegality of the behavior. The four existing evaluation models, namely the comprehensive evaluation model, the uniform conviction model, the typical type model and the hierarchical strength model, are all difficult to accurately judge the degree of illegality of child molestation. In order to solve this problem, a scoring mechanism for the degree of illegality should be adopted for judging the degree of illegality of traditional indecent behaviors such as penetrative indecent behavior and contact indecent behavior. This mechanism classifies the violation parts and the violated parts as the standard, enumerates the different degrees of illegality corresponding to different combinations of behaviors, and assigns a certain score according to the degree of illegality, and then corresponds the score to the qualitative nature of the behavior and the range of sentencing. Finally, a quantitative research method was used to conduct a regression analysis on 494 verdicts to verify the feasibility and effectiveness of the operation of the scoring mechanism.