The invention discloses a low-friction-resistance high-temperature-resistant gelled acid and a preparation method thereof. The method comprises the following steps: 2-acrylamide-2-methylpro panesulfonic acid is dissolved into deionized water, and caustic soda flakes are added, so as to enable the pH value of a system to be 8-10; monomer acrylamide, dimethyl diallyl ammonium chloride and long-chain cationic monomer are added, and then deionized water is added again to prepare into an aqueous solution with the mass percent of total monomers of 25-30%; inert gas is fed in, an initiator is added, and reaction is performed, so that a gelling agent is prepared; a beaker is filled with water, and hydrochloric acid, the gelling agent, a corrosion inhibitor WLD-31A, a ferrous stability B-180 and a petroleum deemulsifier AP-221 are added, so that the low-friction-resistance high-temperature-resistant gelled acid is prepared. The preparation method disclosed by the invention is simple, the production cost is reduced greatly, the prepared gelled acid is 45-56% in retardance ratio, 57% in resistance reduction ratio, and excellent in high-temperature resistance; when the gelled acid is cut constantly for 2 h under the temperature of 120 DEG C, the viscosity is maintained about 50 mpa.s, and acid etching crack length can be increased effectively.