Aiming at the problems of poor retarding effect and difficult injection of retarding acid during the acidizing in high-temperature carbonate reservoir，a retarding thickener（CPAM）was prepared by using dimethyldiallylammonium chloride， acrylamide，K₂S₂O₈ and NaHSO₃ as raw materials. A dual retarding acid system was prepared by compounding CPAM，retarding agent （dodecyltributylphosphine bromide），and retarding dispersant （urea）. The retarding effect and acid etching fracture conductivity of the dual retarding acid at high temperature were studied. The retarding mechanism was analyzed by scanning electron microscopy and contact angle measurement. The results showed that the retarding acid mainly depended on CPAM and urea to improve the film adhesion effect of retarder on the rock surface，and then achieve the purpose of retarding. The optimum formula of dual retarding acid system was obtained as follows：1%—2% retarder，0.1%—0.3% CPAM，1.5% urea. At a temperature of 90 ℃ and a shear rate of 170 s^-1，the viscosity of fresh acid and residual acid corresponding to dual retarding acid system after shearing was less than 10 mPa·s. The retarding efficiency was up to 97% at 90 ℃，which was obviously superior to that of gelling acid. In the high temperature environment of 180 ℃，it had high conductivity retention rate and high-pressure resistance. The dual retarding acid had the advantages of easy injection，high temperature resistance and excellent retarding performance，which was suitable for the acidizing transformation of deep and ultra-deep carbonate reservoir above 180 ℃.