The dynamics and performance of hydropneumatic fender were studied. A theoretical model of the hydropneumatic fender was established to calculate its reaction forces and energy absorption capability. The influences of the length, diameter, volume percentage of water, and the internal air pressure upon the mechanical properties were analyzed. The reaction force and energy absorption capability of the hydropneumatic fender were numerically studied with the finite element analysis software MSC.Dytran. The numerical results were in agreement with the theoretical results, which showed that the theoretical model has well accuracy and is significative for the design of the hydropneumatic fender.