Abstract: To learn if damage effect of a scale-down torpedo warhead can be used to predict that of a prototype warhead for destroying underwater target, based on the similarity theory, some models are established with same scales in war-head size, testing distance of shock wave, and distance of target plate. The shock wave pressure and target plate strain are calculated and compared by simulation and underwater explosion experiment. The calculation and experiment results coincide well, and the deviations of corresponding shock wave pressure and target plate strain of the models are very small, which indicates that the scale-down models following the similarity law can accurately predict the destroy char-acteristics of the prototype warhead against underwater target. This study may provide a basis for the power evaluation of underwater warhead.