With the developments of past 30 years, people working in the civil engineering area have stand on an very important historical node: to establish the third generation design theory of structures. This paper briefly addresses the historic clues of the first and second generations of structural design theory and discusses the basic contradictions associated with the second generation of structural design theory. The characteristics typically featured by the third generation of structural design theory is then illustrated and basic framework are proposed as well. It is point out that the theory of solid mechanics, the modern numerical computational methods and probability density evolution theory consist of the three milestones of the third generation design theory of structures. The primary objective of the third generation of structural design theory is to achieve the global reliability design of structures in its life cycle such that a scientific quantification description can be drawn upon the global safety and service reliability of engineering structures. Ongoing work towards completely building up the third generation of structural design theory is outlined.