The study showed the process of behavior modification of a 6-year old girl with disruptive behaviors, admitted to child-adolescent psychiatry ward. The behavior problems which were observed for a week in the ward were. 1. Without reason, hitting and biting other children and therapists for 10-12 times a day. 2. Rejecting meals and throwing away the tray for 2-3 times a day. 3. Rejecting the drug with aggressive behaviors to therapists. 4. Rejecting to wash her face and brush her teeth with aggressive behaviors to therapists. 5. Taking away other children`s goods without consent for 5-6 times a day. Through the application of behavior modification program, reinforcement and punishment were given simply, definitely. So the adaptive behaviors improved and maladaptive behaviors decreased. The outcomes were, 1. The hitting and biting behavior decreased for 1-2 times. 2. The rejecting meals and throwing away the tray disappeared. 3. She took the medicine without aggressive behaviors. 4. With a little prompt, she washed her face and brush her teeth. 5. Taking away other`s thing decreased for 1-2 times. In addition, other positive behaviors increased. For example, she took care of the younger ones in the ward and could do other activities of daily living. Finally, through the consistent B. M. program at home during admission period, her mother had confidence of controling her daughter`s behaviors.