The present invention provides a method for preparing functional cellulose capable of greatly increasing the effective content of functional materials in fibers. In a cellulose material product obtained according to the method, functional materials account for 5-60% of a relative product mass ratio, or even more, which generally can reach 15% or more or 30% or more. The functional cellulose prepared accordingly can be greatly improved in effects, such as flame retardance, bacteriostasis, moisturizing, skin care, beauty, heat storage and release, aroma, catalysis, and inhibition due to the high content of the functional materials. The method according to the present invention has widely available raw materials, is environmentally friendly during the whole process, is easy to industrial production, and can be applied to fields such as textile manufacturing, medicine, cosmetics, and agriculture.