In order to investigate the blast mitigation effect of the water wall, a numerical model was developed by commercial software LS–DYNA, and its accuracy was validated by the experimental results. Based on this calibrated model, the mitigation effects of the scaled water wall height, the scaled water wall thickness and the scaled water/charge distance (the scaled distance between the explosive charge and the water wall) on the peak incident overpressure and the impulse of the blast wave were analyzed and discussed. A theoretical analysis model based on one-dimensional non-steady flow theory was proposed, and the attenuation of the peak incident overpressure using the water wall was calculated and compared with experimental and numerical results. Moreover, the mitigating mechanism of the water wall was also discussed with the theoretical model. The study results suggest that the water wall is a potentially promising method for the blast mitigation.