He hailed from Xiangping 襄平 (modern Liaoyang 遼陽, Liaoning) and was an office runner in the commandery (jun 郡) of Xuantu 玄菟 (in the territory of the modern DPR Korea North), where his father had fled to in earlier years. Governor (taishou 太守) Gongsun Yu 公孫琙 was highly impressed by him, cared for his education and gave him a daughter to his wife.
Gongsun Du made a brilliant career, was appointed director in a ministerial office (shangshu lang 尚書郎) and then regional inspector (cishi 刺史) of the province of Jizhou 冀州.
In 189 CE, when Dong Zhuo 董卓 usurped the power of the central government, Gongsun Du was recommended by his native collegue Xu Rong 徐榮 and was made governor of Liaodong 遼東. Because Gongsun Du was a humble origin he had often been dispised by the rich landowners and the influential families in the region of the northeast.
When he became governor, therefore, Gongsun Du took revenge for earlier humiliations. He had publicly flocked to death the magistrate (ling 令) of Xiangping 襄平, Gongsun Zhao 公孫昭, and extirpated the family of Tian Shao 田韶 and many other gentry clans. With these brutal methods he was able to ensure the obedience of the local elites.
In 190, when the Yellow Turban rebellion 黃巾起義 haunted northern China, Gongsun Du foresaw the disintegration of the Han empire and decided to make himself independent, with the support of his advisors Liu Yi 柳毅 and Yang Yi 陽儀. He invaded the kingdom of Koguryŏ 高句麗 (one of the three Korean kingdoms) and attacked the tribes of the steppe people of the Wuhuan 烏桓 in the northwest of Liaodong. In this way Gongsun Du expanded his territory and became the dominant political figure in the northeast.
He divided the commandery of Liaodong in three parts, namely Liaodong 遼東, Liaoxi 遼西 and Zhongliao 中遼, and appointed governors for the two new administration units. Later on he even sent a naval expedition to occupy the district of Donglai 東萊 in the northern part of the Shandong peninsula, where he appointed a regional inspector of his newly created "province" of Yingzhou 營州. The commanderies of Xuantu and Lelang 樂浪 also came under his jurisdiction. So strengthened in his power he decided to adopt the title of Marquis of Liaodong 遼東侯 and regional governor (mu 牧) of the province of Pingzhou 平州.
When Cao Cao 曹操 became the strong man in the centre of the empire he bestowed upon Gongsun Du the title of "General of martial authority" (wuweji jiangjun 武威將軍) and gave him the title of District Marquis of Yongning 永寧鄉侯. Yet Gongsun Du refused the title of District Marquis with the argument that he was the factual king of Liaodong, a position that no one at the Han court was able to challenge. He died in 204.
Gongsun Kang 公孫康, the oldest son of Gongsun Du, was in his early years a squad leader (wuzhang 伍長) and inherited the office of governor of Liaodong from his father. Cao Cao defeated the Wuhuan 烏丸, 屠柳城, whereafter Yuan Shang 袁尚 and Yuan Xi 袁熙, sons of the usurper Yuan Shao 袁紹, fled to Liaodong. Yet Gongsun Kang had both executed, as well as the khan of the Wuwan, Supuwan 速樸丸. Cao Cao made Gongsun Kang Marquis of Xiangping 襄平侯 and made him General to the Left (zuo jiangjun 左將軍). When Cao Cao's son Cao Pi 曹丕 (known as Emperor Wen 魏文帝, r. 220-226) made himself emperor of the Wei dynasty 曹魏 (220-265), he bestowed Gongsun Kang with the title of Minister of War (da sima 大司馬).
Gongsun Gong 公孫恭, a younger son of Gongsun Du, had been made District Marquis of Yongning. After the death of his older brother Gongsun Kang, Gong took over the office of governor of Liaodong, because Kang's sons Gongsun Huang 公孫晃 and Gongsun Yuan 公孫淵 were still under age. Emperor Wen of the Wei dynasty made him general of chariots and cavalry (cheji jiangjun 車騎將軍) and conferred upon him the title of Marquis of Pingguo 平郭侯. In 288 his nephew Gongsun Yuan 公孫淵 usurped this position.
Gongsun Yuan 公孫淵, son of Gongsun Kang, was by Emperor Ming 魏明帝 (r. 226－239 CE) bestowed the title of General spreading heroism (yanglie jiangjun 揚烈將軍) and confirmed his position as governor of Liaodong. Gongsun Yuan initiated diplomatic relations with the empire of Wu 吳 (222-280) in southern China, and was rewarded by Sun Quan 孫權 (r. 222-252), emperor of Wu, with the title of King of Yan 燕. Emperor Ming of the Wei empire later made him Minister of War (da sima 大司馬) and granted him the title of Duke of Lelang 樂浪公. In 237 Gongsun Yuan rebelled against the Wei empire, called himself the King of Yan, and created an administrative structure of an independent state. Yet a year later Sima Yi 司馬懿 was ordered to punish the rebel. Gongsun Yuan was defeated and executed.