The invention provides a preparation method of xanthan gum copolymer nano micelles. The preparation method comprises the following steps that after degradation, dynamic viscosity of xanthan gum with concentration of 0.5w% is reduced to 110 mPa s, then after dried, crushed and screened, the xanthan gum is dissolved in N, N-dimethyformamide, a N, N-dimethyformamide solution of 2-bromoisobutyryl bromide is added, a small amount of triethylamine is added for reaction, after obtaining brominated xanthan gum through a method of precipitation, the brominated xanthan gum is dissolved into N, N-dimethylformamide, diacetone-acryloamide is added, under the condition of no oxygen, tri[2-(dimethylamino)ethyl]amine and cuprous chloride are added to be reacted, a xanthan gum copolymer is obtained througha method of precipitation, and dissolved in a polarity organic solvent to obtain a copolymer mother solution, stirring is conducted and water is dropped into the copolymer mother solution until a micelle solution is formed, and through dialysis, the xanthan gum copolymer nano micelles are obtained. According to the preparation method, the prepared xanthan gum copolymer nano micelles have good morphological regularity, good biocompatibility and stable performance as an anti-cancer drug carrier.