Amaranth spinosa is as high as 100 cm, with erect stems, many branches, hairless or slightly pilose. Leaf blade rhombic-ovate or ovate-lanceolate, glabrous or slightly pilose along veins when young; Petiole is glabrous, panicle is axillary and terminal, bracts at the base of axillary flower cluster and terminal flower spike become sharp spines, those at the upper part of terminal flower spike are narrowly lanceolate, midvein is green, bracteoles are narrowly lanceolate, perianth segments are green, cell fruit is oblong, and seeds are nearly spherical, black or brownish black.

Amaranth spinosa is as high as 100 cm, with erect stems, many branches, hairless or slightly pilose. Leaf blade rhombic-ovate or ovate-lanceolate, glabrous or slightly pilose along veins when young; Petiole is glabrous, panicle is axillary and terminal, bracts at the base of axillary flower cluster and terminal flower spike become sharp spines, those at the upper part of terminal flower spike are narrowly lanceolate, midvein is green, bracteoles are narrowly lanceolate, perianth segments are green, cell fruit is oblong, and seeds are nearly spherical, black or brownish black.