Due to the emphasis on the environmental and health issues caused by petroleum-based plastics, renewable lignocellulosic materials emerge as promising substitutes. However, their practical application remains hindered by unsatisfactory properties such as fragility and sensitivity to water. Dealing with the challenge of non-thermal processing of xylan and addressing the issue of performance degradation resulting from the hygroscopicity of materials. In this work, the xylan-graft-poly (methyl methacrylate) (X-g-PMMA) copolymers with adjustable structure and properties were prepared via supplemental activator and reducing agent atom transfer radical polymerization (SARA ATRP). Subsequently, xylan-g-PMMA plastic can be obtained by hot-press. The graft chain length and density were controlled by regulating the monomer concentration and the bromine content. The star-shaped structure of the polymer leads to a significant increase in both the mechanical strength and oxygen barrier properties of the plastic, with the strength at break and modulus reaching 48.35 ± 4.11 MPa and 23.0 ± 0.93 GPa, respectively, and the oxygen permeability reaching 0.389× 10