Abstract: The report, delivered at the 19th National Congress of the Communist Party of China(CPC), points out that, after finishing building a moderately prosperous society in all respects, China will embark on a new journey toward building a modern socialist country. Basing on it, four basic judgements have been put forward and point that 2020 will see a new historical turning point in China. During the new long march of building a modern socialist country, as a core socialist theory with Chinese characteristics, theory of socialist modernization will guide to solve the vast problems ahead. So when Chinese will just cross the threshold of a modern socialist country, the study of the theory of the socialist modernization is significant and imminent. The socialist modernization is rich in connotations. They have two main subjects:what kind of socialist modernization it is and how we should go about doing it. The path of the five modernizations is the only path to the socialist modernization. The theory of the socialist modernization must be the main themes after the 19th National Congress of CPC, even the 20th National Congress of the CPC. Hence accelerating efforts to study the theory the socialist modernization is well prepared for developing China into a great modern socialist country in theory.