How does Chinese state media construct nationalistic propaganda against developed Western countries, and what drives its variation over time? This thesis explores this question by applying topic modeling and regression-based causal analysis to over 40,000 nationalistic paragraphs from People's Daily, published between 2000 and 2024. It identifies two major strands of nationalist narratives—one rooted in insecurity and the other in superiority—and examines how international conflict, diplomacy, and domestic protest shape their evolution. The findings show that propaganda systematically responds to both domestic and international dynamics, but in differentiated ways depending on narrative type and geopolitical context. This study offers a new framework for understanding how authoritarian regimes strategically adapt nationalist messaging in response to global events.