Emperor Suzong of Tang (AD 711-762), personal name Li Heng, was the third son of Emperor Xuanzong. He was conferred the title Prince of Shan first, and then the Protectorate General to Pacify the West in the fourth year of Kaiyuan Period (AD 716). Later, the crown prince Li Ying was deposed, and Li Heng became the successor. In the fifteenth year of Tianbao Period (AD 756), An Lushan captured Tongguan, and Emperor Xuanzong fled to Sichuan. Then Li Heng ascended the throne at Lingwu (Now southwest part of Lingwu, Ningxia), changed the reign title to "Zhide", and honored Emperor Xuanzong as the Overlord.

Taking advantage of the internal conflict between An Lushan and Shi Siming, Li Heng appointed Li Bi in an important position, made Guo Ziyi the vice marshal, and borrowed thousands of soldiers from the Huihe regime with shameful conditions to crack down the rebellion, and recovered Chang'an and Luoyang. In the first year of Baoying Period (AD 762), Empress Zhang and Li Xi, the Prince of Yue, plotted to put eunuchs to death. Unfortunately, the plot was disclosed, and Empress Zhang got killed. The eunuchs put Li Yu on the throne. Emperor Suzong died from worry and shock, and was buried at Jianling Mausoleum (Now Mount Wujiang, 18 li northeast to Liquan County, Shaanxi Province).