This research aims to find out the reason why did United States want to defeat Saudi Arabia in terms of oil and how the relations between United States and Saudi Arabia before the “Oil War” begin and how the impact of the oil war towards the relations between United States and Saudi Arabia. The writer is interested in analyzing the history of oil war and the conditions of United States – Saudi Arabia Relations. The writer believes that oil war is become the big problem for both countries. Saudi Arabia feels defeated by United States, a new kind of oil and gas which is produced by United States is one of the reasons why oil war happens. It may affect the relations of both countries. The finding of this research shows there are two main reasons to explain the cause of oil war between United States and Saudi Arabia. Firstly, both parties now become the great oil countries. Secondly, United States defeated Saudi Arabia and made the price of Saudi Arabia’s oil down.