Summarize the three ways of ancient central government to maintain the unification of autocratic empire and make a brief analysis.

The central government implements the formulation of three provinces and six ministries, and absolutely strengthens imperial power. This began in the Sui Dynasty and lasted until the Ming and Qing Dynasties. In fact, the current central control is also based on the ancient system.

The local government adopts the county system, and the central government appoints officials. Since the unification of China from the Qin Dynasty, it has been used for generations. Now it is also a provincial, city and county level local management.

Imperial examination began in Sui Dynasty, perfected in Tang Dynasty and cancelled in Qing Dynasty. It provided a rising channel for the elite in China and maintained the stability of the dynasty. The current civil service examination is also deeply affected.