The invention provides modified xanthan gum, a preparation method thereof and a fracturing fluid containing the modified xanthan gum. A molecular structure of modified xanthan gum provided by the invention is as shown in a formula (I) defined in the specification. Modified xanthan gum is prepared by performing etherifying modification on xanthan gum by a quaternary ammonium salt etherifying agent, and belongs to cationic modified xanthan gum. According to modified xanthan gum, the viscosity and viscoelasticity of a modified xanthan gum aqueous solution can be remarkably improved in comparison with those of a xanthan gum aqueous solution through electrostatic interaction of negative and positive ions and hydrogen bond interaction of molecules, so that the consumption of xanthan gum can be greatly reduced in use. According to the non-crosslinked fracturing fluid containing modified xanthan gum and prepared from modified xanthan gum as a thickener or a main thickener, the thickener consumption can be reduced and the viscosity of the non-crosslinked fracturing fluid can be enhanced, so that the production cost is greatly reduced.