The invention discloses hydroxypropyl carboxymethyl sesbania gum and a preparation method of the hydroxypropyl carboxymethyl sesbania gum. The preparation method comprises the following steps of taking isopropanol as a solvent, adding sesbania gum powder, triethylamine and alcohol into a reactor, uniformly stirring, dropwise adding a sodium hydroxide solution at the room temperature for stirring for 30 min, raising the temperature to 55-75 DEG C, dropwise adding epoxy propane and a chloroacetic acid aqueous solution for stirring and reaction for 100-180 min, after cooling to the room temperature, performing suction filtration, washing for thrice with wash, and performing vacuum drying to form the hydroxypropyl tianqing gum. The hydroxypropyl carboxymethyl sesbania gum comprises the following raw materials in parts by weight: 30-50 parts of sesbania gum powder, 10-15 parts of sodium hydroxide, 2-4 parts of triethylamine, 10-12 parts of epoxy propane and 8-10 parts of chloroacetic acid. The preparation method is simple, convenient and feasible, extensive in raw material source and low in cost, and has better sand-carrying performance, gel breaking performance and the like.