When underwater explosions with different explosive equivalent are conducted near water surface,bubble movement has certain effect on water surface morphology.Thus,the formation of water spike of free surface,which is critical to this effect,was studied by establishing a bubble motion model of underwater explosion.And the model was realized based on ALE algorism and ANSYS software.More specifically,the morphological changes of the free surface spike,bubble motion characteristics and surface fluctuation characteristics induced by underwater explosion were analyzed by normalizing of time parameters under the conditions of same water depth and distance parameter and different TNT equivalents.The results show that the formation types of the spikes of free surface are in order of fragmented water spike,splash water spike,cup-shaped water spike and crown-shaped water spike with the increase of water depth and distance parameter.At the same time,the cavity radius of the spike of free surface also increases gradually with the maximum value for the cup-shaped water spike.At the same water depth and distance parameter,charge quantity has little influence on the basic morphology of water spike.However,with the increase of charge amount,both the first cycle time of bubble pulsation and bubble radius increase.The vertical displacement of bubble center point gradually moves upward after the first period of bubble contraction.In addition,greater charge amount also increases the characteristic width of crown-shaped water spike and the height of the center water column.The height of the surface fluctuation is increases gradually,and the normalized moment of the maximum surface fluctuation also advances continuously.