Cheating policy on monetary economics is performing surprised inflation, (inflation more than expected inflatin). Barro and Gordon (1983), as the pioneers of cheating policy on monetary economics, in a framework of loss function by using a game reputational model, show that among discretion, rule and cheating policy, cheating is best policy. After that, many studies have done on the legalization of cheating policy. In this paper, by descriptive analysis, we survey the foundation of Barro and Gordon’s model (1983). According to holy Quran and hadith, we show that, instrumental rationality is not acceptable for policy making. As the relationship between governments and people is based on principles of velatat and justice, therefore, cheating policy is forbidden in sharieh of Islam. We then, present an expectation mechanism based on in sharieh of islam and show by this mechanism, both monetary discretion and rule policies would lead more social benefit that the Barro and Gordon’s model (1983). Also, we show that, relaxing enterprises. condition of cheating policy depends on the social expectations of justice, by economic