Hydroxypropyl guar was hydrophobically modified by1-bromotetradecane. The modified product was characterized by FTIR and thermogravimetric analysis. Then, a composite fracturing fluid composed of mass fraction of 0.15%modified hydroxypropyl guar and mass fraction of 0.8% Gemini surfactant, 1,3-N-bis(3-dodecylpropanamide)-1,1,3, 3-N-tetramethyl isopropanol-1,3-ammonium dibromide was prepared. The heat and shear resistance, rheological property, dynamic proppant transport capacity, interfacial property, and formation damage of the composite fracturing fluid were investigated. The results showed that the hydrophobic carbon chains were connected to hydroxypropyl guar successfully. The composite fracturing fluid exhibited good thermal stability with a viscosity of over 109 mPa·s at 90 ℃ and typical viscoelasticity and favorable dynamic proppant transport. The oil/water interfacial tension of the broken fracturing fluid was 0.9 mN/m, which could significantly enhance the hydrophilicity of reservoir rocks. The loss rates of matrix permeability for the oil phase and crack conductivity were only 9.1% and 5.3% respectively.