The resources of the National Development Fund play a major role in financing important projects, and considering the substantial financial need for financing in the oil and gas industry, financing the oil and gas industry from the resources of the National Development Fund, with the cooperation of banks, is helpful. But there are some ambiguities in this regard. Therefore, the main research question is: what is the best method of bank's involvement in financing?

The findings, represent that the nature of bank's involvement in providing loans is as an agent, and as for the nature of the relationship among the Fund, the agent bank, and the receiver of the loans, it can be said that a triangular relationship with different logic of private and public law has developed, and this relationship is completed by adding a fourth element called a specialized insurance company.

In the author's view, applying the advantages of non-participatory contracts, law Participation, and mixed equity-debt by utilizing the agency role of specialized banks in the oil and gas industry for financing oil and gas projects is appropriate, but is still not enough under the current conditions. The joint investment method with other investors, comes in the form of non-intervention investment models with the cooperation of specialized banks in the oil and gas industry in the capacity of a specialized coordinator and strategic partner, together with a specialized insurance company, has more compatibility with the needs and priorities of the oil and gas industry and, is more efficient.