Abstract: Initial pH treatments had evident effects on the growth,cellulose-degrading activity and relative cellulose-degrading activity of Bacillus sp.DS3.The alkaline （pH8.0） favored the growth of Bacillus sp.DS3,and had the highest relative cell density in steady state than other pH treatments.But the pH appeared significant higher cellulose-degrading activity and relative cellulose-degrading activity than those of pH 7.0 and pH 6.0.The results showed that the cellulase activity or production of Bacillus sp.DS3 would be achieved the highest under alkaline,and therefore the initial pH should be about pH 8.0 when DS3 was used to produce cellulase and treat forage high-cellulose-contained.