This book unprecedentedly and systematically puts forward the double helix methodology in think tanks, which is used to explore and answer the questions regarding the pathways and methods to realize the transitions from empirical to scientific research, from discrete to systematic approaches, from random to normative practices, from academic to academic-practical purposes, from static to steady-state analysis, and from mono-disciplinary to interdisciplinary research. The methodology analyzes the evolution trend of research methods in domestic and foreign think tanks and develops the four-layer model of the double helix methodology in think tanks. Revolving the ten key issues of the double helix methodology in think tanks, the book develops the theoretical foundation and methodological guidance for accelerating the formation and development of the discipline of think tank science and engineering and for promoting the professional, scientific, and disciplinary construction of think tanks.