In the sheep and cattle`s rumen, facultative anaerobic cellulolytic bacteria were isolated by using Hungate`s roll tube technique. In the 21 isolated species, one was screened by its strong cellulolytic activity and identified as Cellulomonas fimi C-14 by investigate morphological, cultural, physiological characteristics and electron microgram. Optimum conditions of the cell growth and enzyme production were pH 6.5 and 30℃, Thiamine and biotin support a good growth of C. fimi C-14. In the enzyme activities, Crystalline cellulose hydrolyzing activity, CMCase activity and β-glucosidase activity were 20.6, 226.6 and 0.56(unit×10³/㎖) at pH 6.0, 40℃. By addition of fungal cellulase, enzyme activity was increased. Simultaneous Saccharification Fermentation is better than two step fermentation in ethanol yield with Saccharomyces cerevisiae DY 2.