In order to explore the interaction mechanism between the structure of different sizes and the bubbles,an underwater explosion experiment of 2.5 g TNT was carried out at the bottom 15cm of the fixed square plates with side lengths of 20 cm,40 cm and 70 cm.Through the observation of the experimental high-speed video and the pressure data measured by the sensor,it is found that when the size of the plate is too small,the bubble will contact with the air during the expansion process,and the bubble pulsation process will be terminated.In order to further explore the matching relationship between the explosion bubble and the target size,CEL algorithm in Abaqus software was used to establish the fixed square plate with Lagrange grid and the remaining part with Euler grid.The dynamic behavior and pressure data of the near-field underwater explosion bubble were numerically simulated.The feasibility of the simulation method is verified by comparing the simulation results with the bubble phenomenon captured in the experiment and the measured pressure time history curve.Taking the explosion depth divided by the maximum bubble radius as the specific depth and the side length of the board divided by the maximum bubble radius as the side length,a series of simulations were carried out with the side length of the board being 0.455 to 3.182 times the maximum theoretical bubble radius and the explosion distance being 0.455 to 1.136 times the maximum theoretical bubble radius.The simulation results show that with the decrease of plate size,the bubbles are more likely to collapse in advance.With dimensionless plate size and dimensionless explosion depth as variables,a boundary function is given to complete the bubble pulsation.The closer the distance between explosion distance and plate size,the earlier the end time of bubble pulsation.