In this study, a co-rotating twin-screw extruder was used to conduct the heterogeneous reactive extrusion by in situ modifica- tion of cellulose in the presence of BMIMCl as plasticizer and urea, PA, MA or BGE as modifier. Under high shear stress, the movement of modifier to cellulose chains was improved and the hydrogen- bonding interaction of cellulose was decreased. Compared to other modifiers, anhydride group has higher reaction activity with the hydroxyl group of cellulose, so the regularity of cellulose chains and the hydrogen bond between cellulose chains was destroyed effectively by the grafting reaction of cellulose with PA and MA. Moreover, the smaller molecular weight and less steric hindrance of MA favored the entrance of MA into the cellulose phase and increased the DS, so cellulose-g-MA exhibited lower crystallinity and better thermal stability than other modified cellulose and the spinning solution of cellulose-g-MA showed higher concentration and better spinnability. The in situ heterogeneous modification through reactive extrusion method may provide theoretical base for the industrial production of cellulose fiber with low energy consumption and high properties.