Plants ca. 10 cm tall. Rhizomes decumbent, slender, scales dense, dark brown. Fronds approximate; stipe dark castaneous, glossy, 3-6 cm, as slender as silk, smooth above base; lamina 2-pinnate, narrowly ovate to lanceolate in outline, 3-5 × 1-2 cm, apex obtuse; pinnae 4 or 5 each side, horizontally or obliquely spreading; rachises, costae, and stalks same as stipe; pinnae below middle only, ± uniform in size, imparipinnate, narrowly ovate in outline, 1-1.5 × ca. 0.8 cm; pinnules alternate, with short, slender stalks, spreading obliquely upward, uniformly obtriangular, ca. 4 mm, progressively slightly smaller distally, herbaceous, green, both surfaces glabrous, sterile pinnules: base symmetrically cuneate, bilateral margins straight and entire, upper margins divided and sharply serrate, apex rounded, fertile pinnules with apex truncate or with few sharp serrations on bilateral acroscopic corner; veins multidichotomously forked and reaching margins, visible on both surfaces. Sori 1 per pinnule, horizontally attached at upper margin; false indusia glaucous or dark brown, elongate, nearly as wide as upper margin of pinnule, membranous, upper margins truncate or slightly undulate, persistent. Perispore indistinctly granular.

Adiantum fengianum is listed as endangered in the IUCN Red Book (China Plant Specialist Group 2004. In: IUCN 2012. IUCN Red List of Threatened Species. Version 2012.2. ; accessed 16 Apr 2013).

● Wet rocks in forests; ca. 3400 m. N Yunnan (Lijiang, Yulong Shan).