Cellulose bearing wastewater from pulp black liquor(COD 6 000～8 000 mg/L) is difficult to be treated microchemically. The design and effect of microbial hydrolysis on the pulp black liquor treatment have been analyzed. It is indicated in practice that the sludge concentration in hydrolysis pond is 6. 5～7. 6 g/L, the volume load reaches 4. 2 kg/(m³·d), and the COD, SS removal rate can be up to 28%～38%, 54%～68%. The increment in VFA is 3. 4～4. 7 times, and in BOD/COD is 13%. Compared with coagulating deposition, microbial hydrolysis has the same effect, but the biochemical capacity of the wastewater is improved to a certain extent and the running expense is lessened by 93%.