Abstract: To establish a rapid calculation model for the shock wave of spherical charges in confined space, the shock wave waveform was simplified as a triangular wave. By using the mirror-source method and the LAMB superposition principle, the wall reflection was equivalently represented as the linear superposition of the original and the mirror image explosion sources at the observation point, from which the composite overpressure time history at the observation point was derived. The reliability of this method was verified through comparison with numerical simulation results, with a calculation error of less than 15.92% and a reduction in calculation time of 91.5%. Further, this method was applied to study the influence of different aspect ratios on the peak overpressure at the two-sided corner and three-sided corner of spherical charges in confined space. The results show that the peak overpressure of the shock wave decreases with the increase of the distance from the original explosion source and tends to be stable; the shock wave superposition at the corner increases with the increase of the aspect ratio, and the high-pressure area expands. When the aspect ratio is greater than 1.3, the peak at the three-sided corner exceeds that at the two-sided corner and the direct reflection area. Based on the above rules, this research can provide theoretical reference for the size design of confined spaces.