By discovering the basic relationships among private investment and others macroeconomics Variables, this research try to formulate an Islamic economic theory which consists with the economic doctrine of Islam.

This Study analyzed theoretically the effects of Islamic rules and values in the economy. The prohibiting of Riba (Interest), Iqtinaz (Hoarding) and the control of Alsarff (Exchange) will make the monetary system more efficient. The imposing of Zakah and prohibiting speculation will increase the supply of inactive capital.On the other hand the impacts of Islamic distribution system and the norms of consumption controlled with Islamic values raises the effective demand and leads to expand the size of market. Moreover this study took the account all these factors on the elasticity of aggregate supply.

Private investment should be directed toward the activities which maximize profits within the Islamic rules and the Islamic priorities.

The main conclusions would be summarized as follows: First of all increasing in the real investment and capital formation. Secondly Stability in the investment expenditure which keeps the economy away from business cycles, and Finally investment should be highly related with the real needs of the Islamic society