This paper aims at investigating bank guarantees in Iranian law and exploring new and different bases for the nature of bank guarantees that create liabilities and make accepting this legal action simpler for community members. In other words, we have been in a position to answer these questions: What is the nature of bank guarantees? In other words, do bank guarantees include civil or commercial guarantees? Finally, according to the proposed principles and introduced ideas, it seems that bank guarantees cannot act as a Civil or Commercial Guarantee. It should also be acknowledged that bank guarantee letter is an innovative financial tool that is very important in commercial contracts and in particular international contracts, because they minimize economic risk of the contract and are strong executive guaranty. In general, no contract can be executed or take effect without bank guarantees and insurance.