AM/AMPS/MAC/APEG copolymer was synthesized using acrylamide （AM），2-acrylamido-2-methyl propane sulfuric acid （AMPS），Chloride N-allyl- N-methyl morphine moiety（MAC）and Acrylic polyether （APEG）as raw material. The structure of the copolymer was studied by IR and ¹H NMR，and the influence of reaction condition on the anti-swelling ratio of the prepared copolymer was investigated. In the end，the inhibition ability of the prepared copolymer solution and the copolymer/KCl complex system was probed under different conditions. The reaction conditions were optimized as followed：total monomers content was 20% ，the monomer mass ratio of AM/AMPS/MAC/APEG was of 90∶5∶3∶2，the initiator （sodium sulfite / ammonium persulfate ， molar ratio1∶1）content was 0.2%（based on the monomer mass），the pH value was 4，and the reaction temperature was 40℃. The synthesized polymer had good inhibiting ability. It was found that the anti-swelling ratio of the prepared copolymer solution with the concentration of 2 g/L was over 79% ，and it also could inhibit the swelling stress of illite. What`s more ，the complex system con -taining 30g/L the prepared copolymer and5 g/L KCl could improve the indentation hardness retention of the shale in water from 21.7% to 69%.