In order to solve the contradictory problem of solubility and cross-linking performance of the existing modified guar gum as a water-based fracturing fluid material，a fracturing fluid thickener dihydroxypropyl modified guar gum（DPHG）was synthesized by reaction of 3-chloro-1，2-propanediol and guar gum. The structure of the DPHG was characterized. The physical and chemical properties of the DPHG and its application performance in water-based fracturing fluids were also investigated. Research results showed that content of water insoluble substances of DPHG could effectively be reduced，the dissolution rate could be increased， and the crosslinking performance with boron crosslinking agents could be improved. In the formulation application of fracturing fluid，DPHG showed better temperature resistance，lower usage and residue content than that of the existing modified guar gum. By optimizing the design of the substitution degree of DPHG，the fracturing fluid could be obtained with temperature resistance of 160 ℃，and the residue content of the fracturing fluid after gel breaking could be reduced to below 20 mg/L，which indicated that DHPG had good application prospect.