The invention discloses a polyacrylamide gel oil displacement agent with high toughness. The polyacrylamide gel oil displacement agent is prepared from the following components in parts by mass: 100 parts of acrylamide, 0.03-0.05 part of persulfate, 0.5-8 parts of a multifunctional crosslinking agent solution, 0.002-0.04 part of organic amine and 200-320 parts of deionized water, wherein the multifunctional crosslinking agent solution is an aqueous solution prepared from polyethyleneimine and allyl glycidyl ether or glycidyl methacrylate; the polyacrylamide gel oil displacement agent is prepared by dissolving the acrylamide into water to prepare an acrylamide aqueous solution, adding the multifunctional crosslinking agent solution and the organic amine, adjusting the pH value of the solution to 8-10, adding the persulfate as an initiator at the temperature of 5-30 DEG C, carrying out a heat insulation polymerization reaction under the protection of inert gas, and continuously carryingout the reaction for 1-4h at 50-90 DEG C after gelation of a system. The polyacrylamide gel oil displacement agent has excellent long-term anti-aging performance under high temperature and high salt environment, and is beneficial to application in tertiary oil recovery.