Gulf of Mexico(GoM) is the earliest deep-water oilfields that have been developed. Especially after the 2010's BP oil leakage accident, more and more efficient, safe and inexpensive development key technology have been put into use in this area. Therefore, researching on this important deep-water area tends to be reference valuable to development of deep-water oilfields all over the world. This paper analysis the developing concept in recent 10 years and the EPC contract price of deep-water ocean engineering construction expenditure in GoM. By running the biggest cost database of software QUESTOR and analyzing the cost data of result, the analysis and forecast have been done for the deep-water oil and gas development expenditure in GoM, exploring the relevance between the cost index and oil price.