Strengthening the evaluation of public R&D programs is an important means to promote China’s governance capacity in S&T area. The evaluation activities of public R&D programs in China have been enriched continuously, which has put forward higher demands on evaluation theories and methodologies. Based on foreign evaluation theory tree, by analyzing the evaluation cases of typical public R&D programs in developed countries and region like the US and EU, this study proposes a triangle evaluation model for public R&D programs. It includes key evaluation questions, methods, evidence, and the relations among them. Advantages and shortcomings of 10 evaluation methods in practice are described then, such as peer review, bibliometric, case study, network analysis, etc. Typical evaluation evidence and some using rules are introduced. Finally, this article discusses the significance of the triangle model for improving public R&D program evaluation. It concluded that, along with the trend of science and technology development, as well as the innovation of R&D program model, science and technology evaluation need further reform, handling the basic elements of evaluation is an important principle to meet the opportunities and challenges. The triangle evaluation model and the foreign cases can provide insights for China.