Abstract: The underwater explosion bubbles expand and contract several times until it runs out of energy, during the pulsations, the mutual conversion of energy occurs. At present, there is insufficient attention paid to multiple pulsations characteristics and energy conversion of underwater explosion bubbles. In this paper, the underwater explosion experiments of 20g, 40g, and 60g aluminized charges were carried out, and the evolution process of the bubbles multiple pulsations were photographed with a high-speed camera, then pulsation period and maximum radius of the bubbles were obtained after intelligent processing. On this basis, the theoretical analysis was conducted on the conversion mechanism of the potential energy, internal energy during the multiple pulsations. The results show that: (1) the residual energy rate of the second bubble pulsation relative to the first bubble pulsation was 0.31; (2) the proportion of internal energy of the bubbles to total energy is 5.4%-6.6%, so the internal energy could be ignored, and energy of the bubbles could be represented by the potential energy in the engineering application.