In recent year, international crude oil price fluctuates dramatically, which greatly exceeds the amplitude of fluctuation estimated by most research institutions and academics. In order to cope with high uncertainties and risks during oversea oil and gas project development, it is necessary to conduct an intensive study on oversea oil and gas project evaluation. Starting from international oil contract and the parameters of economic evaluation and based on the main parameters of economic evaluation in the international oil and gas cooperation, Monte Carlo analysis method is applied in contract quantitative analysis. The results show that economic evaluation results obtained by using Monte Carlo simulation are more accurate and flexible than deterministic evaluation results. This study indicates that international oil and gas cooperation economic evaluation based on Monte Carlo simulation will be more accurate. Especially in such external conditions with significant fluctuation, the results of economic evaluation based on Monte Carlo simulation can provide more comprehensive references for oversea oil and gas project investment decision-making.