Abstract: Severe heterogeneity and microfractures developed in Changqing Triassic reservoir, acidizing fluid enters into high permeability zone or microfracture in ordinary acid treat which expands water passageway, and water content ratio increases enormously after acid treat. In view to the problem, a new self-diverting acidizing of viscoelastic surfactant SUA-3(Gemini quaternary ammonium salt) was developed, as a result of SUA-3 molecular structure has two alkyl and quaternary ammonium salt, the formulation fluid of SUA-3 has favorable viscoelastic behavior. The viscosity increases to 460 mPa·s rapidly reacting with calcium carbonate at 60℃, and when the pH value increases to 6, the viscosity decrease to 78 mPa·s rapidly after meeting with crude oil. So the system is self-diverting in place and acid can distribute uniformly and break viscosity voluntarily. It was applied in oil field with a remarkable stimulation effect.