Abstract: Aiming at the problem of double secondary reservoir that conventional acidizing fluid could not reach deep reservoir in Moliqing Oilfield, the oil phase, water phase, emulsifier and oil/acid ratio were optimized, then a new kind of emulsified acid was developed. The indoor performances of emulsified acid were evaluated by stereomicroscope and core displacement device etc. Results indicated that the reaction kinetics equation of the emulsion was J =1.370 3×10^-6·C^{1.130 4}, which means that the emulsion acid system has obvious retarding performance. The surface tension of emulsified acid was as small as 22.40 mN/m, and its viscosity was a bit bigger than mud acid without emulsification. The vast majority particle size in emulsified acid solution was relatively uniform, and the emulsion system was relatively stable. Core permeability after acidification by emulsified acid was 10 times as before acidification. Core permeability after acidification by emulsified acid was more than 3 times of mud acid. Viscosity value and surface tension value of reacted acid was relatively small, contributing to clean-up.