With the application and promotion of large-scale biogas project, economic analysis and evaluation of large-scale biogas project are particularly important. However, the benefits of biogas project embodied in the economic, social, ecological, and many other aspects have dispersion, which leads to production decisions in a gray state and investment in conformity. In this paper, Great Northern Wilderness beef cattle industry in Heilongjiang province is taken as an example for large-scale biogas electricity generation project. The supply and demand of funds in project operation are analyzed quantitatively by using system dynamics theory so as to do study and perform optimal analysis comprehensively on the economics of biogas project, and to explore the effective scheme of improving the proportion of income against cost. This study can provide scientific guidance for evaluating the construction and operation of large and medium-scale biogas project objectively and lay a solid theoretical foundation for the commercial operation in biogas industry.