Abstract: After Shang Yang's reform, Qin Dynasty, whose military system evolved from the pentadimal system of the Zhou Dynasty to the decimal system, grew stronger and stronger. In the course of putting in place the system of merit titles established by Shang Yang, two changes have taken place. One was that the first sixteen titles have changed into twenty titles by adding two titles of Chehou and Guannei to the upper ranks, and the two captains of the Qin army, Si Chong and Si Chechang came into being. For one thing, the title of nobility became a new kind of official position, and the official title became the command system of the Qin army. Qin Shi Huang separated the titles and restored the officer command system.

Key words: Qin Dynasty, military meritorious service, duke of system, formation