In traditional Chinese historiography, he was presented as a minimally competent ruler who devoted much of his time to feasting and pleasure-seeking, neglecting the affairs of the state.
[1] In 565, he passed the throne to his young son Gao Wei, taking the title Taishang Huang (retired emperor), but continued to make key decisions.
At their public wedding ceremony, Gao Zhan was said to be appropriate in his actions despite his young age, surprising the guests.
During this period, Gao Zhan closely associated with He Shikai and Zu Ting, even calling them brothers—and both of them would eventually have key roles in his administration.
Meanwhile, the ambitious Yang was carrying out a governmental reorganization scheme to trim unnecessary offices and titles and to remove incompetent officials.
Yang, Kezhuhun, Yan, Zheng, and Song Qindao (宋欽道) were all seized and severely battered (at Gao Zhan's order).
Emperor Xiaozhao continued to take up residence at Jinyang, again leaving Gao Zhan in control at Yecheng.
In spring 562, Emperor Wucheng created his wife Princess Hu empress and her son Gao Wei crown prince.
When Gao Guiyan got to Ji Province, his subordinate Lü Sili (呂思禮) reported him as planning a rebellion, and Emperor Wucheng sent the senior generals Duan Shao (段韶) and Lou Rui (婁叡) against him; they quickly defeated him, and he was executed along with his sons and grandsons.
She suffered severe injuries, but eventually recovered, and Emperor Wucheng expelled her from the palace to be a Buddhist nun.
He Shikai stated to Emperor Wucheng: Emperor Wucheng, persuaded, entrusted the civil service system to Zhao Yanshen (趙彥深), financial matters to Gao Wenyao (高文遙), the civilian administration over military affairs to Tang Yong (唐邕), and the education of Crown Prince Wei to Empress Hu's brother-in-law Feng Zicong (馮子琮) and cousin Hu Changcan (胡長璨).
Emperor Wucheng sent the general Hulü Guang (Hulü Jin's son) to resist the southern prong of the Northern Zhou attack, and personally went to Jinyang to resist the northern prong, but when he got to Jinyang, he was surprised by how strong the Northern Zhou and Tujue forces were, and he considered fleeing, stopping his flight only after opposition by Gao Rui and Gao Xiaowan (高孝琬) the Prince of Hejian.
Also in spring 564, the one major accomplishment of Emperor Wucheng's reign—a revision of Northern Wei's criminal code—was completed, allowing greater fairness in the application of laws.
Further, Emperor Wucheng was interested in greater promulgation of the laws, and he ordered the children of officials' households to study them, leading to a wider base of legal knowledge than previously had been the case.
At that same time, Gao Bainian's teacher Jia Dezhou (賈德冑) submitted several instances of the character chi (敕) -- a character that meant "imperial edict," and which only the emperor was supposed to use—that Gao Bainian had written, to Emperor Wucheng.
Despite Duan's suggestion that he negotiate formal concessions, Emperor Wucheng, in fear of Yuwen Hu's anger, released Lady Yan in fall 564.
Due to Gao Wei's young age, Emperor Wucheng continued to be in control of major decisions, despite his "retirement."
In spring 568, Emperor Wucheng suffered a major illness, and the official Xu Zhicai (徐之才), who was an accomplished physician, treated him back to health.
Before Xu could arrive, however, around the new year 569, he died, while holding He Shikai's hands and entrusting the important matters to him.