The invention relates to a guar gum polymer containing hydrophobic group and carboxymethyl prepared by kneading method with guar gum sheets as raw materials in the pressing crack technology of the oil field. Hydroxypropyl guar gum used as densifier at present has the disadvantages of high broken gum residue content of pressing crack liquid system, slow viscosity recovery after high shear on hydroxypropyl guar gum pressing crack liquid and weaker high shear resistant performance. The invention provides a guar gum polymer containing hydrophobic group and carboxymethyl prepared by kneading method with guar gum sheets as raw materials. The guar gum consists of ethanol, guar gum sheets and the like. The method comprises the steps: spraying a mixed solution of alkali lye and ethanol through a jet pipe onto the guar gum continuously stirred on the kneader; adding chloroacetic acid; sprinkling brominated tetradecane/ethanol mixing solution; heating, keeping the temperature, tackifying, and inneutral washing reaction vessel washing, centrifuging, drying, crushing. Thus myristyl grafted carboxymethyl guar gum is obtaine. The modified guar gum of the invention has the excellent characteristic of temperature resistance, salt resistance, shearing resistance, sterilization and the like.