In his youth, he served in the army of Pinglu Circuit (平盧, originally headquartered in modern Chaoyang, Liaoning but later moved to Weifang, Shandong).
It was said that at the time, many senior generals were expecting themselves to be put in charge in the operation against Liu, and that when Gao was announced as the commander, many were surprised.
While passing through Xingyuan Municipality (興元), the capital of Shannan West, there was a soldier who got angry at a restaurant and destroyed the chopsticks he was using; Gao immediately put him to death to maintain discipline.
[3] By the time that Gao reached Zi Prefecture, it had fallen, and Liu had taken the military governor of Dongchuan, Li Kang (李康), captive.
[3] Meanwhile, Liu constructed eight defensive fences at Lutou Pass (鹿頭關, in modern Deyang, Sichuan) to resist Gao.
When it was suggested to him that he offer Liu's two beautiful concubines to Emperor Xianzong, he believed that doing so for imperial favor was improper; instead, he gave them to two of his officers who were not married.
[2] It was said that as Gao was illiterate, he disliked the frequent paperwork that was involved in overseeing the prosperous city of Chengdu, and he often requested to be transferred to a border region.
[2] In 807, Emperor Xianzong had the chancellor Wu Yuanheng replace him, and moved him to Binning Circuit (邠寧, headquartered in modern Xianyang, Shaanxi).
Emperor Xianzong also made him the overall commander of the troops west of the capital Chang'an and gave him the honorary chancellor title of Tong Zhongshu Menxia Pingzhangshi (同中書門下平章事).