After the financial crises of 2007 – 2012 banking and financial policy – makers applied some reforms in the financial markets. One can label these items rationalizing financial market. Regarding high attention of Islam to rationality principles one can rationalize the usury – free banking model as well. The Precondition to compile such model is the realness of software and hardware Platforms including transparency of   financial information and the possibility of controlling financial transactions. So one objective of this paper is to analyze the challenges of Iran banking system to  substitute it with  financial rationalism. One   finding of this research shows that in order to have any progress in standardizing  usury free banking, we can go ahead  in direction with moderate rationality.  In so doing Iranian banking system would benefit from rational banking at one hand. It would be  compatible with Shariah at the other