Although customs can't be the source of criminal law to criminalize or inculpate, they still often affect the constituent elements of crime. Therefore, in the field of criminal law, the existence of customs can't be ignored. In this article, we try to discover, from the practical case, that judicial decisions have no complete principles when facing customs that leads to different results in the end. Thus, through broadly discussions on customs in criminal law, and review the judicial practices, we try to find out the relationship between customs and justification for criminal offenses beyond statute and provide a guideline for public references.