Rhizomes long creeping, apex clothed with brownish ovate-lanceolate scales. Fronds distant; fertile fronds 18-40 cm; stipe stramineous, 11-25 cm, 0.5-1 mm in diam., base sparsely scaly, upper part glabrate; lamina 2-pinnate to 3-pinnatifid, deltoid-ovate, 7-13 × 4-8 cm, herbaceous or papery, base rounded, apex acuminate; pinnae 5-8 pairs, opposite, oblique, basal 3 or 4 pairs stalked, articulate to rachis, basal pair largest, narrowly triangular, 4.5-8.5 × 3-4.5 cm at base, base subtruncate, with stalk 6-13 cm, slightly oblique, pinnate, apex acuminate; pinnules 4-6 pairs, opposite or subopposite, deltoid-lanceolate or narrowly oblong, base broadly cuneate, basal 1 or 2 pairs articulate to costae, subsessile, apex acuminate; basal basiscopic pinnules longest, descending, 1.5-2.7 cm × 6-8 mm, pinnate or pinnatipartite; pinnule segments 5-7 pairs, oblong to narrowly ovate, separate or adnate at base, crenate, apex rounded-obtuse; second basal pair of pinnae 1.7-3.3 cm apart from basal pinnae, narrowly triangular, much smaller than basal pinnae, 2-5.5 cm; third and upper pairs of pinnae broadly lanceolate, gradually smaller; veins pinnate in segment, simple, sometimes forked, oblique, visible; stipe (at least upper part), lower part of rachis, costae, and midribs pubescent with short glands. Sori small, orbicular or oblong, abaxial on veins, submarginal, exindusiate.
One of us (Pryer) notes that Gymnocarpium robertianum (Hoffmann) Newman (Phytologist 4: append. xxiv. 1851; Polypodium robertianum Hoffmann, Deutschl. Fl. 2: add. et emend. 10. 1795), which was treated as conspecific with G. altaycum in FRPS (3(2): 70-71. 1999), is glandular on both sides of the upper stipe, firm and stiff in texture, and moderately glandular on the adaxial as well as the abaxial surface, including on the laminae.