A st rain of ext remely t hermophilic, anaerobic, xylanolytic bact erium w as isolated f rom t he hot spring in K angding County, Sichuan Province, and it was gram reaction negative, immobile, non sporef ormative w ith it s cells arranged single or in pairs, 0. 7 1. 0 m w ide and 2. 0 5. 0 m long. Af ter being cult ured at 75 f or 3 d on xylan agar rolling tube, it s colon ies w ere roun ded, convex, smoot h in margin and t ransparent , and could not produce pig ment s, but could produce carbon dioxide, hydrogen, lact ic acid, acet ic acid and t race et hanol during t he fermentation of xylan.Keywords: thermophilic, xylanolytic bacterium.Xylan is a major component forming hem icellulose and accounts f or 50% of dry w eight of herbaceous plant s. Its sources are very abundant in the world. Xylan is firstly hydrolyzed int o sm all molecular x ylose, and then t he x ylose can be ut ilized by m icrobes in m at erial cycle. T here are tw o w ays f or hydrolyzing x ylan; t hat is, acid hydrolysis and enzy molysis. T he enzy molysis not only possesses high transformat ion rate, requires m ild condit ions, produces no erosion, no toxicit y and no environment pollution, but also has low cost s and easy operat ion [ 1] . In recent years, t he enzymolysis of x ylan has been w idely used for t he t reatment of wastes, product ion of chemicals, x ylose and xylitol [ 2] . Part icularly t he enzymolysis is of great import ance and of large economic value in environment al prot ect ion, for it can replace chemically bleaching t echnology in pulp and paper product ion [ 3] . T he st udies on thermost able x ylanase originat ing from microbes have caused great at tent ion in the w orld and some papers have been published on several strains of Bacil lus genus w ith optimum g row t h t emperat ure of 65 [ 4,5] . T his paper presents t he studies on t he morphology and grow th properties of t he ex tremely t hermophilic, alkalophilic, anaerobic, xylanolyt ic bact erium isolat ed f rom the hot spring in Kangding, Sichuan. Materials and methods Source of sam plesT he samples for t his experiment w ere collected from t he sediment s in t he hot spring in Kangding, Sichuan. Serum bot tles of 50 mL were prepared and filled w ith hig hly pure nit rogen. Samplers w ere used t o put the sediments and w at er into t he bot tles. T he volume of the mat erials filled accounted for 4/ 5 of t he tot al volume of t he bot t les. During t he performance, air was not al lowed to ent er into t he bot t les.