Abstract: The dynamics of underwater manipulator with many degrees of freedom is much more complicated if hydro-dynamic terms are precisely treated.The dynamics is important for the robot system simulation and feedback control design,so the finger dynamics of dexterous underwater hand is analyzed based on the strip theory,and the precise dynamics model is established considering the drag force and added-mass force.Dynamic simulation is carried out using SimMechanics.The results show that the hydrodynamic forces make the finger deflect from the required trajectory,and these parameters must be considered in the dynamic motion control.