The endurance of empire in China over much of the past two millennia contrasts starkly with the political fragmentation in Europe since the fall of Rome. To explain the persistence of China’s empire, we analyze the role of keju, the imperial civil service examination system. We argue that the systematic implementation of keju from the Song dynasty onward tied local elites to the imperial state, sustaining political integration and reducing secessionist conflicts. Exploiting panel data covering 4,243 grid cells and 22 centuries, we find robust evidence that areas producing more jinshi – the top exam passers – experienced significantly fewer secessionist wars. Our study shows how the examination system created the political incentives for imperial durability.