The emperor was the title of the supreme ruler of China during the imperial period. In ancient times, Huang Xi Fuxi, Wa Huang Nuwa, Huangdi Xuanyuan and Yan Di Shennong were not real emperors, but only tribal leaders or tribal alliance leaders, and their titles of "emperor" or "emperor" were added by later generations. Xia dynasty monarch called "Hou", Shang dynasty monarch called "Emperor" and Zhou dynasty called "Wang". During the Warring States period, most governors claimed to be kings and respected Zhou as the "heavenly king". Ying Zheng, king of Qin, unified China, thinking that he was "a Huang San with both ability and political integrity, and made contributions to the five emperors", and created the word "emperor" as the official title of the supreme ruler of China.