This paper undertakes a comprehensive comparative study of two of the world’s most influential constitutional documents—the Constitution of the United States (1787) and the Constitution of the People’s Republic of China (1982, amended through 2018). Although both claim to embody the will of “the people,” they represent fundamentally different traditions of constitutionalism shaped by divergent historical, ideological, and political trajectories. The U.S. Constitution reflects liberal-democratic principles rooted in Enlightenment thought, emphasizing limited government, separation of powers, individual rights, judicial independence, and federalism. In contrast, the PRC Constitution institutionalizes socialist governance under the leadership of the Communist Party of China (CPC), prioritizing collective welfare, state-directed development, and democratic centralism.Historically, the U.S. Constitution emerged from struggles against monarchical authority and sought to restrain governmental power through checks and balances. The PRC Constitution grew out of revolutionary struggles, national reconstruction, and ideological consolidation under Marxism–Leninism and its subsequent Chinese adaptations. Structurally, the U.S. system divides authority among coequal branches, whereas China’s system fuses authority under the CPC, with the National People’s Congress as the supreme state organ in form but operating under party leadership in practice.