Herbs, perennial, 30-75 cm tall, often caespitose; rhizomes robust, branched; roots long, thick, collar clad with marcescent leaf bases. Stems erect, simple or branched, sparsely to sometimes moderately villous, moderately to densely minutely stipitate glandular, leafy. Leaves basal and cauline; cauline leaves gradually reduced, abaxially sparsely villous or glabrous, moderately to densely minutely stipitate glandular, adaxially sparsely villosulous or sometimes villous, moderately to densely minutely stipitate glandular, margin entire or serrate to serrulate, sparsely to moderately villosulous-ciliate, densely minutely stipitate glandular, midvein abaxially prominent, veins conspicuous; basal leaves withered at anthesis; basal and lower cauline leaves ± broadly winged petiolate (petiole to 6 cm) or lower leaves sessile; blade ovate to oblanceolate, (5-)7-18 × 1-4 cm, base attenuate, apex acute to obtuse; middle cauline leaves sessile, lanceolate or oblong to oblanceolate, 5-16 × 0.8-6 cm, base rounded or cordate to auriculate, semiamplexicaul, apex acute, sometimes obtuse. Capitula terminal, solitary or 2-9 in lax corymbiform synflorescences, 4-8.5 cm in diam.; peduncles 4-16 cm, sparsely to moderately villous, densely minutely stipitate glandular. Involucres hemispheric, 1.5-2.5 cm in diam.; phyllaries 3-seriate, subequal, ovate-lanceolate to linear-lanceolate, 10-16 × 0.8-4(-5) mm, densely white villous basally and glabrate above or sparsely villous distally, or sparsely villous along veins, or glabrate, moderately to densely minutely purple stipitate glandular, membranous, margin narrowly scarious, erose, purple, distally ciliate, multiveined, apex acute to acuminate, purple-tipped. Ray florets 65-125, pale purple to purple-blue, tube apex and lamina base minutely stipitate glandular, tube 1.6-2 mm, lamina linear, 20-30 × 1-2.5 mm, glabrous; disk florets yellow to orange, 5-5.6 mm, tube 1.8-2 mm, tube apex and base of limb minutely stipitate glandular, limb narrowly funnelform, ca. 3.5 mm, lobes erect, triangular, 1-1.2 mm. Achenes (immature) narrowly obovoid, compressed, 3-4 mm, sparsely strigillose, sparsely minutely stipitate glandular distally, 4-ribbed. Pappus 3-seriate; outermost series of broad scales 1-1.2 mm, white or straw-colored; bristles barbellate; inner bristles acute; innermost bristles ca. 6.5 mm, weakly clavate. Fl. Jul-Sep, fr. Sep-Oct.

Aster yunnanensis is closely related to A. diplostephioides but differs in having usually branched stems, usually broader phyllaries (rarely somewhat narrow), and disk florets apically yellow, not purple. Based on variations in width and indumentum of the phyllaries, this species can be divided into the following varieties. Grierson (Notes Roy. Bot. Gard. Edinburgh 26: 67-163. 1964) did not segregate A. yunnanensis var. angustior and A. yunnanensis var. labrangensis.

● Alpine and subalpine grasslands or meadows, forest margins, slopes, seepage areas, cutover mixed forests, scrub, pastures; 2300-4500 m. Gansu, Qinghai, Sichuan, E and S Xizang, Yunnan.