The range runs in a roughly northeast to southwest direction, roughly from Guangyuan near the province's northeastern border, to the western part of the Chengdu Prefecture, in the central part of the province, where it approaches the southern end of the Qionglai Range.

The uplift of the Longmen Mountains is a result of vertical slippage on the Longmenshan Fault.

The Longmen Mountains represent the eastern rim of the immense Tibetan Plateau.

Some maps use the name "Longmen Mountains" only for the northeastern section of the range, while the taller southwestern section is labeled Chaping Mountains (Chinese: 茶坪山; pinyin: Chápíng shān).

Jiudeng or Jiudengshan (Chinese: 九顶山; pinyin: jiǔdǐng shān; lit.