To solve the problems that cement slurry can not stay，is easy to be diluted by water，and is poor in cementing strength and plugging effect for blocking the malignant leakage in large cracks，vug and aquifer，a quadripolymer gel was prepared by copolymerization of acrylamide（AM），2-acrylamide-2-methylpropanesulfonic acid（AMPS），N-vinylpyrrolidone（NVP）and hydrophobic monomer（MJ-16），and the gel was further added to cement slurry to form a gel-cement slurry composite leakage plugging system. The water dilution resistance，rheology，retention capacity and compressive strength of the composite system were studied. The results showed that the gel had good rheological property and temperature resistance. The system formed by gel， cement，retarder and defoamer had a fluidity of 21 cm and adjustable thickening time，and can be pumped safely. The system was still integrated under water and had good resistance to water invasion，resulting in it was not diluted by water at the stirring speed of 150 r/min. Moreover，the system had good retention capacity，as a result，the time of the system to pass the 1 mm crack was more than 10 times that of the ordinary cement slurry，and the system could stay and stack at the entrance of the leak layer，as wells as the compressive strength reached more than 7 MPa. The gel-cement system was especially suitable for the leakage plugging of large channels，large fracture holes，underground rivers and aquifers.