Which emperor of the Tang Dynasty moved the capital to Luoyang?

Wu Zetian.

In the first year of Tianshou (690), Wu Zetian proclaimed himself emperor, changed the name of the country to Zhou, made Luoyang the capital, called the "Shen Capital", and established Wu Zhou. Before and after his reign, he was "clearly aware and good at making judgments", had many powers and strategies, knew people well and appointed them well, attached great importance to the selection of talents, and created the system of imperial examinations, military examinations and official examinations.

Also rewarded farmers and mulberry trees, and reformed the administration of officials. At the same time, the Tang Dynasty clan was massacred and "cruel official politics" emerged. Militarily, the four towns of Anxi were recovered, and the Turks surrendered for a time. In his later years, he gradually became extravagant and arbitrary, and developed bad governance.

Extended information:

The reason why Wu Zetian moved the capital to Luoyang

First of all, from a political point of view, since Wu Zetian wanted to become emperor, she might want to avoid it in her heart. From the Li Tang Dynasty. After all, with new things and new atmosphere, she wants to change the government, so she seems to be starting anew politically.

Economically speaking, Luoyang is the most prosperous. Based on the Beijing-Hangzhou Grand Canal opened by Emperor Yang Guang of the Sui Dynasty, Luoyang is even more prosperous and its economy is far ahead. Moreover, both land and water transportation are very convenient, which should be one of the reasons why Wu Zetian moved the capital.

Baidu Encyclopedia-Wu Zetian