Du was born to an eminent aristocratic family in what is now Xi'an, Shaanxi, almost eighteen years before the abrupt rebellion of An Lushan, and received office for the privilege as administrator of Chi-nan commandery (modernly Licheng District).
Robert G. Hoyland considers him a "political thinker on a grand scale," comparable to Ibn Khaldun, but he is most often remembered for his thirty-six year compilation of the Tongdian, a historical encyclopedia of 200 sections (volumes) collecting laws, regulations, and general events from ancient times to his own.
[3][4][5] While considering Confucian teachings on the relationship between father and son essential, Du stated that he didn't believe that they provided relevant information for government policy.
A legal specialist and authority over state finances, he became Commissioner for Public Revenue and Salt and Iron, and has been called a "Legalist" for his appreciation of political planners, dismissal of antiquity and concepts like fate, and strong interest in the Xunzi.
[6][7][8] Du You had been impressed by a 35-volume work by Liu Zhi during Emperor Xuanzong's reign known as the Zhengdian, which was a compendium of philosophies, rites, and principles of governance.
[9] Du You's own civil service career started from a position that he was given on account of his heritage — the military advisor to the governor of Ji'nan Commandery (濟南, in modern Jinan, Shandong).
Later, when Wei served successively as the governor of Zhexi Circuit (浙西, headquartered in modern Zhenjiang) and military governor (Jiedushi) of Huainan Circuit (淮南, headquartered in modern Yangzhou, Jiangsu), he continued to invite Du to serve on staff and entrusted Du with many responsibilities.
[9] During the reign of Emperor Xuanzong's great-grandson Emperor Dezong, after Yang Yan became chancellor in 779, Yang had Du recalled to Chang'an, and Du successively served as Gongbu Langzhong again and then as Jinbu Langzhong (金部郎中), a supervisorial official at the ministry of census (戶部, Hubu).
[9] With Emperor Dezong waging multiple campaigns against warlords ruling their circuits in de facto independent manners at the time, Du was forced to raise taxes heavily and force merchants to lend one quarter of their assets to the state to cover the expenses.
Because Emperor Dezong had been forced to flee Chang'an due to a rebellion by Zhu Ci in 783, however, the officials at his makeshift court did not have full knowledge about precedents, and Du became the first military governor of Lingnan not to also be director of the five districts.
While he was serving there, his mother died, but Emperor Dezong recalled him from his mourning period to continue his service.
After Du arrived in Chang'an in 803, he was made chancellor with the designation of Tong Zhongshu Menxia Pingzhangshi and acting Sikong (司空, one of the Three Excellencies).
[9] It was said that Du was diligent and studious, and even when he reached the apex of governmental service, he continued to study earnestly.