This research work analyzes the characteristics of American public diplomacy from the perspectives of smart power theory, comparing China and the United States’ smart power strategy. The article revealed that globalization and the process of technological evolution have led profound changes in the contempopary world politics and international relations, the smart power factors such as culture, science, technology, and information have become increasingly prominent in political science. These factors have not only created the fundamental theory of smart power, but also affected the form and definition of diplomacy. The research methodology is based on a complex combination of scientific methods, mainly comparative, analytical, systematic. The obtained conclusions can be referred that smart power as a key factor, has become a new theoretical perspective for understanding changes in contempopary international relations and foreign policy. It has naturally become the theoretical support for public diplomacy, meanwhile public diplomacy itself is also an important content and strategic path for smart power construction.