To solve the problem of high friction of emulsified acid and damage of gelled acid polymer residue in carbonate reservoir stimulation，nanoemulsion was prepared using non-ionic surfactant（tristyrylphenol polyoxyethylene ether），cationic surfactant （quaternary ammonium salt），and cosurfactant（alcohol）as raw materials through pseudo-ternary phase diagram. Then，20% HCl， 5% nanoemulsion，0.1% resistance reducing agent（cationic polyacrylamide），and functional additives were mixed to prepare nano homogeneous phase retarded acid. The properties of the homogeneous phase retarded acid were systematically analyzed and evaluated using rotating rock disc instrument，scanning electron microscope，EDS spectrometer，conductivity meter，particle size analyzer，interfacial tensiometer，wetting angle tester，friction tester，acid-etched fracture conductivity meter，and core flow meter. The retardation mechanism，high acid-etched fracture conductivity mechanism and scale dissolving mechanism were analyzed. The results showed that the nano homogeneous phase retarded acid was a kind of nano homogeneous dispersion system with oil in the inner phase and acid in the outer phase. The particle size distribution was 8—100 nm. It had strong retardation（retarded rate greater than 90%），low friction（friction reducing rate greater than 75%），low viscosity，low damage and high acid-etched fracture conductivity. It could dissolve organic scale and inorganic scale simultaneously. The dissolution rate of asphalt and carbonate rock was 6.91% and 100% ，respectively. It could remove the damage from reservoir emulsification，water lock，and wetting modification. Nano homogeneous phase retarded acid adsorbed on the surface of positive electric limestone by negatively charged nanoemulsion，and then the“isolation barrier”between acid and rock was established to achieve strong retardation. Through differentiated acid-etched and viscous fingering，the high acid-etched fracture conductivity was realized. Through the special oil-water miscible structure of nanoemulsion，organic scale and inorganic scale could be removed simultaneously. The system was successfully applied on offshore oilfields with remarkable effect of increasing production，which was of great significance for the deep treatment of carbonate reservoirs and multiple damage removal.