In order to obtain new retention and drainage-aid agent, exfoliated xylan-g-QCS/MMT nanocomposites were prepared. Briefly, quaternized chitosan azide (QCS-N) was intercalated into the layer of montmorillonite (MMT) to enlarge the interplanar gallery; subsequently, QCS-N/MMT was grafted with xylan by click chemistry, during this process, the interlayer space of MMT was further increased till exfoliated. Subsequently, the exfoliated xylan-g-QCS/MMT was evaluated to act as retention and drainage-aid agent. The initial critical concentration of xylan-g-QCS/MMT was 0.01 mg/g in the adsorption behavior on cellulosic substrate. The maximum flocculation efficiency for CaCO was 37.41%. When dosages were about 0.01 mg/g, SR values were the lowest. All these results show that retention and drainage-aid performance of xylan-g-QCS/MMT was better than only xylan, QCS or MMT. The study combined three kinds of natural resources to prepare organic/inorganic nanocomposites, providing a new method to develop papermaking additive and achieve high-value utilization of natural resources.