Abstract: Hydraulic fracturing and matrix acidizing as the stimulation measures for fractured tight sandstone reservoir have their limitations. Acid fracturing technology applied to the target reservoir has obtained the remarkable effect to increase production. For specific reservoir, this paper calculated the shear?slip conditions occurred in natural fractures and simulated the effect of acid fracturing liquid on calcite?infilling fracture and shear?slip fracture by experiment. The study shows that compared with the conventional stimulation operations, acid fracturing mainly relies on the following two effects to obtain high flow conductivity: shear?slip occurs in natural fracture under the action of hydraulic stress, and the surface roughness of fractures can form the self?supporting; acid liquid corrodes the fillings, harmful substances and part of rock matrix to increase residual unclosed fracture space, hence improving the fracture conductivity. On the basis of mechanism study, this paper puts forward implementation suggestion of the process