In the information system, there are many fields that used by decision making support system. Nowadays, the reasons that the need of the decision making system in audit is increased, are as follows. circled1 The increased of competitiveness in audit environment circled2 The rapid replenishment of computer hardware and computer system in corporations. The purposes of this study are as follows. circled1 The connection of Internal management assess results and practical examination. circled2 In the making of audit opinion, the establish of non-measure and evaluate logic. circled3 The suggestion of knowledge base structure about the audit task. circled4 The development of prototype system for the accounting audit expert system. The expected usefulness of accounting audit expert system development are as follows. circled1 Audit time may be saved circled2 The consistence of opinion will be increased circled3 The elevation of audit technique circled4 The decreased of audit risk circled5 In the decision making rationlization of accounting information users, it will be proved as usefulness.