Sihai Township, formerly under the neighboring county of Guang'an City, Sichuan Province, is located in the eastern foothills of the Huayhuash Mountains, east of Heliu Township, south of Chunmu Township, west of Huayhuash Xikou Township, and north of Gamba Township, with an area of 35.75 square kilometers, and a household population of 11,727 as of the end of 2018. During the Republic of China period, it belonged to Hefeng Township.In 1958, the township was changed to a commune.In 1981, it was renamed Sihai Commune.In 1984, the commune was changed to a township.In December 2019, Sihai Township was abolished, and the administrative area it belonged to was transferred to the jurisdiction of Heliu Township. In 2018, Sihai Township had 7 industrial enterprises, including 3 above scale, and 4 general stores or supermarkets with business area over 50 square meters.