Recently in Japan, to build a new community mental health support system, Assertive Community Treatment（ACT）has been trying to implement. In this paper, four problems were discussed. 1）Problems of applying DACTS to Japan. 2）The historical problems of mental health and welfare of Japan. 3）Problems of modern mental health care and welfare systems in Japan. 4）How does the forensic psychiatry in Japan influences the philosophy of ACT.
 As a result,considerable contemplation and preparation is needed to implement the ACT. Following point was proposed to achieve ideal mental health system. We must carry out deinstitutionalization policy（ex. reduction of mental hospital beds, review the budget allocations for mental health system, etc.）before ACT would be implemented.