Abstract: Over the five centuries of the existence of the Roman Republic,the constitutional government had been the focus in the construction of the governing system.The core of the constitutional government was reflected in the balancing spirit of the state power and the social relations,which checked the social classes,political interest groups and the government’s law-enforcing departments.When such a balancing spirit was at work,the various relations within the Republic were kept steady.Once the balancing spirit was destroyed for any reason,the foundation of the Roman constitutional government became shaky,and the Republic was doomed to fall.

Key words: Roman Republic, the constitutional government, the balancing spirit