Although it is not known exactly how long people have lived in the area, it is generally believed that the first inhabitants arrived between 6,000 and 10,000 years ago. Recorded history begins in the early Han Dynasty about 100 BC when Haikou and its surrounding district became part of Daimao County of Zhuya Prefecture.

Haikou City was opened as an open trading port in the late Qing Dynasty and continued to benefit from its role as the island's commercial center and gateway with steady long-term growth. Haikou was proclaimed a city in 1926 and a capital city in 1988 when Hainan was established as a province. Haikou experienced accelerated growth when Hainan was proclaimed China's largest Special Economic Zone in 1988.