The deep carbonate reservoirs in Sichuan Basin are dense, and in general, they show the characteristics of extra low porosity and low permeability, with poor reservoir conductivity, limited length of acid fracture, and great difficulty in remodeling. In order to further increase the single well production capacity and improve the effect of reservoir transformation, this paper carries out experiments with different acid fluids, conducts research on the morphology of acid-etched fractures and the law of conduction capacity, and evaluates the effects of acid rock reaction, acid dissolution, and residual acid injury of different acid fluids, the analytical results show that the acid fluid filtrates out to the natural fracture in the process of acid injection, and the deepening of the etching around the fracture helps to form a non-uniform etching surface, and builds the channel of high conduction capacity, with the number of alternating stages increases, the inhomogeneity of acid distribution inside the fracture is improved, which is conducive to the improvement of the conductive capacity; the conductive capacity of autogenous acid as the alternating fluid is better than that of slip water, and under the conditions of indoor experiments, the reforming effect of the three-stage alternating injection mode of autogenous acid + gelatinized acid is the best. Therefore, for tight reservoirs with poor physical properties, it is recommended to adopt the three-stage alternating injection mode of autogenous acid + gelling acid in the acid pressure process, in which gelling acid is the main acid fluid.