In order to improve the strengthen of inorganic gel and avoid precipitation and separation after adding polymer into inorganic gel，a thermo-responsive composite gel diverting agent was synthesized using low-cost polymerized aluminum ferric sulfate，urea，acryl amide，initiator ammonium peroxydisulfate and cross-linking agent N，N-methylene-bis-acrylamide. The microstructure and distribution state of diverting agent were characterized by using infrared spectrometer and scanning electron microscope. The temperature resistance and washing resistance of composite gel diverting agent were studied. The results showed that the suitable synthesis condition of thermo-responsive composite gel diverting agent was obtained as follows：2.0%—3.0% acryl amide， 1.5%—2.5% polymerized aluminum ferric sulfate， 0.4%—0.8% urea， 0.03%—0.05% ammonium peroxydisulfate， 0.02%—0.04% N， N-methylene-bis-acrylamide， 50—90℃ gelling temperature. The gelation time of this diverting agent ranged from 5 to 36 hrs and the gel strength was higher than 3×10⁴mPa·s. It overcame the deficiency of gelling quickly of common inorganic gel. Because of the low initial viscosity（<10 mPa·s），the diverting agent had favorable injectivity and migration property which achieved objectives of large dose injection and in-depth plugging. The composite gel had good thermal stability with 87.4% viscosity retention rate after aging 120 days at 90℃. The plugging ratio of composite gel was above 98%， and its sealing property and washing resistance were obviously stronger than that of common inorganic gel and organic gel. The thermo-responsive composite gel diverting agent could meet the requirement of profile controlling and flooding in oilfield.