Basionym: Palhinhaea hainanensis C. Y. Yang, Bull. Bot. Res., Harbin 2(4): 141. 1982; P. hainanensis f. glabra H. S. Kung & Li Bing Zhang.
Plants medium-sized to large, terrestrial; aerial shoots erect, up to 30-150 cm tall, terete, middle part 2-3.5 mm in diam., dichotomously branched with well-differentiated lateral branchlets much branched; leaves of aerial shoots spirally arranged, sparse, subulate, ca. 3 × 0.5 mm, thinly herbaceous, midrib indistinct, base rounded, decurrent, sessile, margin entire, straight or slightly involute, apex acuminate. Lateral branches ascending, dichotomously branched with well-differentiated lateral branchlets much branched, pubescent or glabrous; leaves of lateral branches and branchlets spirally arranged, dense, strongly bent upward, subulate, not narrowed toward base, falcate, 2-3 × 0.5-0.8 mm, thickly herbaceous to leathery, with 1-3 longitudinal furrows on surface, glabrous or shortly pubescent, midrib indistinct, base robust, decurrent, sessile, margin entire, apex acuminate. Strobilus solitary, terminal on small branches, often pendulous or slightly pendulous, pale yellow, shortly terete, 3-5 × 2-2.5 mm, sessile; sporophylls ovate-rhombic, imbricate, ca. 0.6 × 0.8 mm, margin membranous, with irregular teeth, apex acute, caudate. Sporangia enclosed.
Forests; 100-300 m. Hainan [Indonesia, Vietnam].
In comparison with leaves of Lycopodium cernuum, those of L. hainanense are broader and shorter, more strongly falcate, with thicker texture.
Branches of Lycopodium hainanense are pubescent or glabrous.