Abstract: To study the motion characteristics of the opposed biconical cone screw seawater hydraulic pump,the displacement and velocity equations of different points on the screw were presented. The motion simulation of points on the screw was also conducted on the basis of the three-dimensional model and virtual assembly. Analysis shows that trajectory of the screw spherical section center is prone to a straight line with smaller basal cone's half cone angle; trajectories of different exterior surface points are spherical ovals in different sizes; displacement and velocity's components on each axis of the screw spherical section center and its exterior surface points vary periodically,and variation period on x-axis and y-axis is equal to the time in which screw runs a circle,while the screw runs half a circle on z-axis;when the displacement of above points reaches its minimum,the velocity reaches its maximum,and vice versa.