With the increasing global outlook of Chinese petroleum enterprises, their decision-makers face a series of risks. Economic risk analysis is an effective means of reducing losses. Based on the characteristics of overseas investment projects and system analysis of risk factors, Monte Carlo simulation and decision tree analysis methods are adopted in this paper to evaluate the economic risks for one overseas investment project. The results show that the two methods have almost the same conclusion that the project is low risk. Finally, suggestions are put forward to deal with the economic risks of overseas investment projects.