The history of Haikou originates from Han Dynasty.
In 110B.C. (the first year of Western Han Dynasty), General Lu Bode of Fubo conquered Baiyue, and set two prefectures-Zhuya and Zhan'er-and 16 counties in Hainan. Haikou was under Zhuyadaimao County.

In Tang Dynasty, Haikou became a port of Qiongzhou, and it was the transportation hub to the mainland. In Song Dynasty, in order to consolidate the frontier, Haikoupu was established, hence the name.

In 1858 (the eighth year of Emperor Xianfeng), Haikou was opened up to be a trading port, the name was changed into Qiongzhou kou. After that, the consulates of various countries were set up here gradually. In the early days of the People's Republic of China, its name was changed to Haikou.

It was liberated on 23, April 1950, and the People's Government was founded on June 1, the same year. After liberation, Haikou was a city under the jurisdiction of the provincial government of Guangdong, and was the capital of Hainan administrative.

In March 1983, it was declared to be an open city. In 1988, it became the capital city of Hainan Province.