The invention discloses a method for preparing hydraulic fractured composite fracturing liquid, which comprises the following steps: a. under room temperature, evenly mixing anionic polyacrylamide solution, cationic polymer solution and cosolvent solution according to certain proportion, and slowly stirring the mixture to fully dissolve to form a composite polyelectrolyte solution; b. compoundingthe composite polyelectrolyte solution obtained in step a, modified guargum solution and water according to certain proportion, so as to obtain a composite thickening agent solution with functions ofwater control and oil increment; and c. evenly stirring the composite thickening agent solution obtained in step b, cross linker and non-oxidized gel breaker according to certain proportion, so as toobtain the composite fracturing liquid. The method has the advantages of simple preparation processes and easily controlled reaction conditions; and a composite fracturing liquid system can play a role of fracturing liquid thickening agent, and can also change permeation property of a storage layer or make partial water plugging reach the controlled water-oil ratio.