In this study we used 1-allyl-3-methyl imidazole formate ([Amim][HCOO]) as ionic liquid to pre-treat the cellulose and determined the rate of polymerization and enzymatic hydrolysis. The results showed that pretreatment with ([Amim][HCOO]) significantly decreased the cellulose polymerization. As the pretreatment temperature went up, the enzymatic hydrolysis rate was first increased and then decreased. The maximal enzymatic hydrolysis rate was achieved when the pretreatment temperature was 90°C. Under the ultrasonic condition, the initial rate of enzymatic hydrolysis for the ionic liquid-treated cellulose was up to 11.10 gL-1h-1, which was 33% increase compared to the untreated cellulose. Scanning Electronic Microscopy (SEM) and Fourier Transform Infrared-Raman Spectroscop (FT-IR) analysis showed that ionic liquid- treated cellulose started to depolymerize. In addition, the crystallinity of the cellulose was significantly decreased after pretreatment with ionic liquid.