The cost-benefit evaluation of ecological engineering is an assessment of the effectiveness and rationality of ecological engineering implementation. Based on the cost-benefit theory, this study analyzed the investment cost of the Hulunbuir grassland meadow ecological function area (HGMEFA). In addition, based on the remote sensing and statistical data, we evaluated the comprehensive benefits of the HGMEFA from ecological, economic, and social perspectives and calculated the benefit-cost ratio of the project to comprehensively evaluate the economic efficiency of HGMEFA construction. The results showed that:(1) From 2010 to 2014, the total investment in the relevant fields of HGMEFA construction was 84.31 hundred million yuan, while the construction cost of the HGMEFA was 1.18 hundred million yuan, accounting for 1.40% of the total investment; (2) The contribution rate of ecological construction was 37.25%, and the ecological benefit of HGMEFA construction from 2011 to 2015 was 1.25 hundred million yuan; (3) The economic and social benefits of HGMEFA construction from 2011 to 2015 were 0.49 hundred million yuan and 0.28 hundred million yuan, respectively; (4) The engineering construction benefit-cost ratio of the HGMEFA was 1.71, with benefits higher than the investments, thereby proving that the project was economical. This study will provide scientific support for continuous improvement of the national key ecological function area project and acceleration of the functional orientation of the national key ecological function area.