This paper deals with how system dynamics can be used as a methodology for policy critics. First of all, I discuess conditions that is required as a methodoogy of policy critics. A methodology for policy critics should be ease to be uderstood by lay people. It can be produced within limited time and have high relevancy to the policy reality. By reviewing some examples and literatures, I propose that system dynamics can meet these requirements and thus can be a promising tool for policy critics.