Abstract: Fibriform modified sawdu with larger specific surface area, extended surface area, cumulative pore volume and pore area, total pore volume and absorption ability are manufactured through sawdu pulping process. It is shown from measurement results that explosion properties of rock expanded ammonium nitrate explosive made with this modified sawdu can be improved obviously. Surface characteriic parameters of modified sawdu are teed by BET method, and compared with that of ordinary sawdu. It is concluded from te results that surface characteriic of modified sawdu can be increased greatly, which is the essential reason for increasing explosion properties of explosive.