According to the Hou Han Shu Baiguanzhi後漢書百官志, each Han commandery was placed under a commandery administrator, called Jun shou 郡守, who was assisted by a number of lesser staff. Among them, jun gongcao郡功曹 was the major one. The present research investigates the duties of jun gongcao during Han times and concludes that jun gongcao identified worthy performance, selected staff and acted as the leader of different commandery bureaus. His authority sometimes superceded the commandery administrator's valuable assistants, the cheng丞, who was in charge of all civilian and military affairs in the inner region of the Han Empire, and zhangshi長史, who was responsible for armament and horses in the frontier region. Here the author argues that jun gongcao was obliged to oversee the commandery staff work and the operation of the commandery bureaus. This research also discusses the relationships between the wooden documents excavated in the M6 burial at Yinwan and the duties of jun gongcao in the local administrative system. The author's views are as follows. The deceased of this burial had held the tenure of jun gongcao during his lifetime. He had the opportunity to keep the administrative records as well as the personnel data of the staff at the commandery and prefecture levels. The wooden documents, such as the Jibu集簿, Donghai Jun liyuan by 東海郡吏員簿, Donghai jun xiaxia zhangli mingji東海郡下轄長吏名籍, etc., excavated at Yinwan were within the scope of his duties. He probably made copies from the governmental documents for memorial and when he died his descendants put them in his burial.