Abstract: Though total production increase, oil production drop after routine acidzing in a lot of producer of low permeability reservoir.A new acidzing formula system has been developed in the light of this problem.The mechanism is introduced in this paper.Through model test, the acid system can select priority oil-bearing pore and carry out retarding acidization and deep removing blockage.A large number of experiments result show the system viscosity will increase when the acidzing formula system meet with water and the viscosity will decrease when the system meet with oil.And the oil-emulsion acid interfacial tension is less than water-emulsion interfacial tension.In static behavior, the acidizing velocity of emulsion acid is less than that of routine acid.The experiment results show acidization improvement percent of oil-bearing pore are all over 60% and are below 15% to water-bearing pore.So the formula is effective in removing blockage around well bore in low permeability reservoir.