Li Daozong was probably born in 603, during the reign of Emperor Wen of Sui (Yang Jian). His grandfather Li Zhang () was a Northern Zhou official and a son of the Western Wei general Li Hu (), the grandfather of the major Sui Dynasty general Li Yuan, who had been executed late in Northern Zhou for plotting with the Northern Zhou prince Yuwen Zhao () to kill Yang Jian while Yang Jian was regent and on the path to take over the throne. Li Zhang's sons were not killed, however, and one of them, Li Shao (), was Li Daozong's father.