"Modesty is the essential virtue." Moral education of modesty is significant in shaping healthy personalities, improving mental health and interpersonal relationship. The mode building for moral education of modesty in teenagers consists of four basic aspects: cognition, emotion, motivation and behavior. When applied to practice, it follows these principles: subjective, developmental, instructive, integrative and operational. We should adopt the educational methods of student-orientation, self-improvement, unification of knowledge and action, and improvement from within and without to apply the theory of modesty education to moral education practice.