In this study, a development of a 6 D.O.F underwater manipulator which is actuated by electric motors capable of carrying over 70kg payload. It designed to be driven at 3,000m. Balancing weight is applied to reduce the capacity of the joint-2 actuator. I calculated the ideal motor capacity by interpreting inertia torque where is on the each joint actuator. The joint actuator for the manipulator is designed as a double oil jacket for waterproofness in high pressure. Each link is designed the modularization to assemble and replace the parts easily. The kinematics and dynamics of the manipulator has been analyzed based on new designed manipulator. By doing this, I can figured out the feature of 6-axis manipulator motion and stability evaluation of link structure. Also, Thickness of link cylinder at 3,000m has been verified through FEM simulation.