M5 block is a typical tight carbonate reservoir with low porosity and permeability. The natural productivity of production wells in this kind of reservoir is low, and it is difficult to reach the limit of economic exploitation. In order to achieve a more ideal stimulation effect, the acid fracturing technology is often used as a stimulation measure for such reservoirs. The fracture conductivity after acid fracturing is an important basis to evaluate the effect of reservoir fracturing, and the fracture conductivity is affected by fracture surface morphology, effective stress and other factors. Therefore, here are the great significance to predict fracture conductivity and characterize the nonuniformity of fracture wall under the effective stress for productivity prediction. The core of this block is taken as the experimental research object, and the stress concentration theory in rock mechanics is introduced to establish the conductivity calculation model by quantitatively analyzing the variation law of opening in the process of wall contact. Finally, the model is verified. There are two main modules in this research: such as the digital characterization module of fracture surface and the conductivity calculation module. The obtained conclusions has a certain reference value for improving the effect of reservoir reconstruction in the later stage of production wells in this block.