Sunwu County (simplified Chinese: 孙吴县; traditional Chinese: 孫吳縣; pinyin: Sūnwú Xiàn) is a county under the administration of Heihe City in the north of Heilongjiang province, China, situated on the bank of Amur River, which demarcates the Sino-Russian border.

The length of border line within Sunwu county is 36 km (22 mi).

Sunwu County is surrounded by Lesser Khingan Mountains, and its forest coverage is 45%.

[citation needed] Sunwu County has a monsoon-influenced humid continental climate (Köppen Dwb) with very warm, humid summers and severely cold, extremely dry winters.

There are two towns and nine townships in the county:[4][5] Towns: Townships: 2 Formally part of Oroqen Banner in Inner Mongolia but administered de facto by Daxing'anling Prefecture in Heilongjiang.