Abstract: Project cost management and control is a major problem in some large projects cost hundreds of millions and sometimes billions of dollars from the budget exceeded the forecast is something very disturbing. A crucial factor in the successful completion of each project is to predict the correct fee (P. Smith, 2014). In this study, the methods used to estimate the cost of large hydroelectric dams were studied and then with the help of estimation method (Gordon, 1983) parameter estimates in construction and Msthdat, Accord, machinery and equipment, land, project staff remuneration, other assets not producing and the overall cost of the dam to dam Seimareh, Scroll, Karun 3 and Karun 4 with growth rates of 8%, 10%, 13%, 15%, 17% and 20% in the cost of approved and fees were assessed and finally to estimate appropriate and predictable cost projects, hydropower in two approved and paid the coefficient k (a factor which is based on engineering judgment for each project) in three parts, maximum, minimum and average is calculated