Abstract: When analyzing the trend of international oil price, we need to consider the cost of supply.Breakeven costs under different conditions reflect different needs.The total cost of oil exploration and development supports the breakeven of oil enterprises.The state breakeven oil cost of oil producing countries is an important indicator to measure whether the country can keep economic and social stability.Analysis of state breakeven oil cost can analyze the supply behavior of oil-producing countries and thus predict the price trend, also helps to interpret the policy trend and reform behavior of oil-producing countries and predict the possible political and fiscal crisis.However, in practical application, it is necessary to take the state breakeven oil cost into comprehensive consideration with a country's foreign exchange reserves, exchange rate changes, fiscal policies, geopolitics and other factors.This paper analyzes and calculates the oil national cost of Saudi Arabia, the results show that since 2009, the state breakeven oil cost of Saudi Arabia has been increasing, and after the new cycle of oil price decline in 2014, Saudi Arabia's tightening spending has gradually shown results that the oil national cost of Saudi Arabia has been decreasing, and the gap with the international oil price has been narrowing.