Chuang-Tian CHEN, Academician of the Chinese Academy of Sciences, Fellow of the Third World Academy of Sciences, has conducted research on crystal material science and technology for a long time. He proposed the Anionic group theory of the Nonlinear Optical (NLO) properties of crystals, later known as the NLO active group theory, and has successfully applied it for the search of new types of inorganic NLO materials. The research group under his leadership discovered the new NLO crystals BBO and LBO, which have applications of great importance in industry. Recently, NLO crystals such as KBBF, SBBO and KABO have also been developed which have promising applications in the deep and vacuum ultraviolet region. Chen's group won a first prize of the National Invention Award and a special prize of CAS S&T Progress Award, while he has been given the Laser Focus World Commercial Technology Achievement Award and the Third World Academy of Sciences Award for Chemistry.