In this research, steam explosion is utilized to pretreat Populus tomentosa Carr. Effect of explosion pressure on yield of material, cellulase activity and hydrolysis rate is discussed under the conditions of explosion time 4 minutes and explosion pressures 1.5, 2.0, 2.5 and 2.7MPa respectively. The results are: ① when the pressure is raised from 1.5 MPa to 2.7 MPa, the yield of material dropped from 84% to 51%; ② If steam exploded Populus tomentosa Carr. wood powder with wheat bran is used as car...