The paper proves the necessity and urgency of the thorough study of the “One Country, Two Systems” theory. The idea of “One Country, Two Systems” is an institutional innovation created by Mr. Deng Xiaoping and other Chinese leaders. It has already become one of the basic components of the socialist theoretical setup with Chinese characteristics. And the Macao SAR now becomes a good example of the examination of the “One Country, Two Systems” theory and thinking. Of course, the formulated during last 30 years the mentioned theoretical setup should be continued to develop in the practice in the SARs. The “One Country, Two Systems” theory is subordinated to the basic topics of the modern constitutional science and modern political science. Actually, it has become a new type of mature scientific system, which consists of a lot of important principles including the SAR system. Therefore, it is important for the SAR government and the public to make a systematic and longtime investigation of the “One Country, Two Systems” theory, also the laws of evolution of its practice in the SARs.