The work aims to prepare cellulose nanofibrils with rubber wood as raw material. The cellulose nanofibrils were prepared via chemical pretreatment combined with high intensity ultrasonication. The structure and properties of cellulose nanofibrils were studied with the help of SEM, TEM, XRD, FTIR, TG, UV and universal material testing machine. The diameter of cellulose nanofibrils prepared from rubber wood was within the range of 3~10 nm, with natural cellulose I structure retained and better thermal stability. Moreover, the prepared film had better mechanical properties and transmittance. With rubber wood as raw material, cellulose nanofibrils with similar basic characteristics to poplar cellulose nanofibrils can be prepared by conventional chemical pretreatment combined with high intensity ultrasonication, and have higher yield.