The invention provides an etherification and oxidization method for preparing cellulose nano crystal whiskers. The etherification and oxidization method is characterized by comprising the following steps: taking plant fibers with low cellulose content as raw materials; carrying out pre-treatment, etherification treatment and alkali treatment; carrying out mechanical crushing to obtain plant cellulose powder; carrying out TEMPO oxidization treatment, and stirring at a high speed to obtain a plant cellulose powder suspension solution; and carrying out centrifugal treatment, dispersion treatment, freezing and drying to prepare the cellulose nano crystal whiskers. The etherification and oxidization method has a simple preparation process, high yield and low energy consumption; in a production process, no toxic and harmless substances are discharged, and the method has a large-scale popularization and application potential; the used plant fibers can be jutes, straws, cotton stalk peels and the like, and have a wide raw material source and low cost; the environmental pollution problem is solved and the addition value of the plant fibers is also improved.