Today, considering the risks of investing in huge and expensive projects, especially in countries with little technology, the "EPC" or turnkey contract has presented itself as a standard, attractive and targeted contract in the field of large investments. The following article deals with the analysis and analysis of the adjustment percentage of the contractor's obligations in the engineering, equipment supply and construction contracts, known as EPC, using the analytical and descriptive method. According to the findings of the design and construction and engineering contracts research, the supply of equipment is one of the two-factor contracting contracts, the most important feature of which is the one-dimensional and unilateral responsibility of the contractor. He assumes all possible damages and defects of the project. Although some consider this type of contract to be different from the turnkey contract, it must be stated that most authors do not distinguish between these two contracts. These types of contracts are two-factor contracts, in other words, it is a special form of turnkey contracts in which the employer or his consultants will only be involved in the bidding process and high supervision of the contractor's work. Among the contractual measures to manage the price risk in the EPC contract, using the conditional amount method, the currency-Rial cost method, paying attention to the effect of payment mechanisms on the time and costs of the project