In this study, xylan-graft-polycaprolactone (xylan-g-PCL) with different degrees of substitution (DS) and degrees of polymerization (DP) were prepared by homogeneous ring-opening graft polymerization (ROGP) of e-caprolactone (e-CL) onto xylan in ionic liquid (IL) 1-allyl-3-methylimidazolium chloride ([Amim]Cl) using 4-dimethylaminopyridine (DMAP) as catalyst. FT-IR, 1D (H-1 and C-13 NMR) and 2D NMR (H-1-C-13 HSQC and HMBC) spectra provided the evidence of the occurrence of ROGP reaction. 1H1H COSY confirmed the correct assignment of the proton signals. HSQC also indicated that 38.78% and 61.22% of PCL side chains were attached to C-2 and C3 positions of anhydroxylose units, respectively. Xylan-g-PCL copolymers were further characterized by TGA/DTG, SEM, and XRD. The results indicated that the thermal stability of xylan increased upon the DMAP-catalyzed ROGP reaction in [Amim]Cl, and the surface morphologies were significantly changed with increased DS.