Privatization is one of the major problems in many developing countries, especially Iran, which that following proposes such as competitiveness and economic efficiency, increasing productivity, investment and efficient use of resources. Therefore, study the barriers of proper implementation of privatization and achieving the aims of general policies promulgated by the supreme leader to, is very importance. Accordingly, this paper is looking to answer the question of what factors could be deterrent factor to increase the investment of private sector? In order to answer this question, initially introducing the appropriate model to estimate the effective factors on the private sector investment and then present the results of model by using vector autoregressive method (VAR). the results of Model show that an increase in the government size, permanent (long-term) inflation and exchange rate fluctuations are as an obstacle to increasing the private sector investment (in this study, SME manufacturing). It should be noted that this model is shown the crowding out impact well. Considering that the size of government is one of the major barriers in the way of private sector investment in the economy, therefore, performing the reformed policies of Article 44 seems unavoidable, which has been proposed by the Supreme Leader. Naturally, implementation of the communicated policy will be moderate and remove the other barriers in the way of private sector investment gradually.