It originates in the Guancen Mountains of Ningwu County in northeast Shanxi, flows southeast into the basin of Taiyuan, and then south through the central valley of Shanxi before turning west to join the Yellow River west of Hejin.

Within Taiyuan, the Fen runs from north to south; the prefecture includes one-seventh of the river's course.

The Fen is usually identified with the Ji River said by Sima Qian and others to have flowed beside the home of the Yellow Emperor.

[2] The lower Fen was part of the core area of ancient China and held the capital of the state of Jin near Houma.

The second valley is the Su River, which was along the north edge of Zhongtiao Mountain; and it was forming another triangular basin.

[3] Modern cities on or near the Fen from north to south are: Taiyuan, Linfen, Houma, Hejin.

In the 1990s, the municipal government of Taiyuan built artificial and removable structures across the river at different locations to create reservoirs of water for landscaping purposes.

The surface area of these reservoirs amounts to 1.7 million square meters and, along with newly created vegetation of 1.3 million square meters on the banks, forms the 6-kilometer long Fen River Park.