The Coastal Mountain Range, also known as the Hai'an Range (Chinese: 海岸山脈; pinyin: Hǎi'àn Shānmài), is a mountain range situated on the eastern coast of the island of Taiwan, and spans the border between Hualien and Taitung Counties. Coastal Mountain Range is part of the Philippine Mobile Belt which was formed over 400 million years ago by the collision and compression of Philippine Mobile Belt and Eurasian Plate. The geological structure is composed of soft sediments which have weaker anti-erosion property and are vulnerable to wind.
The Huatung Valley, the result of the collision of two tectonic plates, is at the west end of the range, and the tallest peak of the range is Xingangshan (新港山), which stands 1,682 m (5,518 ft) tall. Currently those peaks are still with an annual speed of 3 mm. The Haian Range is also converging with Central Mountain Range with an average speed of 2.3 cm per year.
There are several small basins located around the range, the largest of which is Taiyuan Basin.