In order to analyze the characteristics of axial distribution of borehole wall pressure along the borehole in rock blasting, the axial distribution of borehole wall pressure along the borehole of coupled charges with different borehole diameters was studied by combining theoretical analysis, model testing, and finite element simulation. Firstly, based on the theory of spherical detonation wave, a model of the detonation wave propagation in the borehole was established. Based on the relationship between the incidence angle of the detonation wave and the diameter of the borehole, the theoretical calculation formula of the borehole wall pressure under different propagation stages of detonation was derived, and the change curve of the borehole wall pressure along the axial borehole wall with different borehole diameters was obtained. In order to verify the rationality of the theoretical analysis, the concrete thick wall cylinder model test was further used to monitor the pressure of the borehole wall by using a high-speed multichannel dynamic strain test system. Meanwhile, finite element numerical simulation of different borehole diameters was established to obtain the axial distribution of borehole wall pressure results of different borehole diameters. And the model test and numerical simulation results were compared with the theoretical analysis results. The results show that the coupled charge borehole wall pressure presents an uneven distribution along the axial direction of the borehole, and the borehole wall pressure near the detonation point increases sharply, begins to decrease exponentially after reaching the maximum peak pressure, and finally tends to fluctuate steadily. There is a positive correlation between the borehole wall pressure and the borehole diameter. The maximum peak pressure and the stable fluctuation stage of the borehole wall pressure increase with the borehole diameter. The relative error between the theoretical calculation value of the axial borehole wall pressure at d=40 mm and the results of the model test and numerical simulation is small, which verifies the rationality of the theoretical analysis.