This book explores the essence of the middle-income trap based on two major perspectives, namely “economic transformation” and “social transformation”. China has experienced high-speed economic growth for nearly 40 years since the adoption of the Reform and Opening policies. However, China’s economic growth has been slowing down significantly in recent years. Has China tumbled into the middle-income trap? This book reveals the essence of the middle-income trap is that a country's economic growth is facing a "double squeeze" in the middle-income stage, while the social structure and system are unsuitable for the new social development stage, which leads to economic stagnation or recession, and the aggravation of social contradictions, that is, the double predicament of economic transformation and social transformation. This judgment is of great value for understanding the problems encountered in the current development of China.