The structure of this idiom is beautifully parallel: 国 (Country) + 泰 (Peaceful) and 民 (People) + 安 (Secure). Together, they create a complete and harmonious image: when the nation is stable and prosperous, its people can live safe and secure lives.
国泰民安 (guó tài mín ān) is one of the most significant concepts in Chinese political philosophy. Its importance is deeply tied to the ancient concept of the “Mandate of Heaven” (天命, tiānmìng). For millennia, an emperor's or government's right to rule was not seen as absolute but was granted by a divine “heaven.” This mandate could be lost if the ruler failed to govern justly and effectively. The most visible sign of a ruler's failure was chaos, famine, and rebellion. Conversely, the clearest evidence of a ruler possessing the Mandate of Heaven was the state of `国泰民安`. This creates a powerful connection between the well-being of the people and the legitimacy of the state, a concept that persists in modern China. The government's performance is often implicitly judged by its ability to deliver this state of national stability and public well-being. Comparison to Western Concepts: While an English speaker might say “peace and prosperity,” there's a crucial difference. “Peace and prosperity” can be a personal goal or a general wish. 国泰民安, however, is almost exclusively used on a grand, national scale. It reflects a collectivist value system where the health of the nation is the prerequisite for individual happiness. It is a top-down concept—a stable state leads to peaceful people—whereas “peace and prosperity” can often feel more bottom-up.
This is a very formal and literary term. You will not hear it in casual, everyday conversation.
Its connotation is overwhelmingly positive and solemn.