The loading characteristics of ship’s double bottom tanks subjected to underwater non-contact and contact explosions were researched respectively using AUTODYN finite element software. The loading type of the double bottom tanks during semi-load and full load conditions was analyzed, and the influence of explosive distance and loading condition on the loading characteristics of internal plate was discussed. The result showed that the transmitted shock wave is the major threat of the inner plate in full-load condition; the splashing loading is the major threat of the inner plate in semi-load and non-contact situation; and high-velocity water-jet is the major threat of the inner plate in semi-load and contact situation. Therefore, the semi-load condition of double bottom tanks is strongly recommended to warship in active time.