The streamline method is an important method in the visualization of 3D vector fields. A view-dependent streamline simplification method for 3D vector fields based on feature-preservation was proposed to solve the problems of streamline occlusion and visual confusion caused by excessive streamlines, and to ensure the streamlines could present the variation law and important features of vector fields exactly. A streamline set of 3D vector fields was generated by particle tracking and was mapped between view-dependents. A feature-preservation computation of the streamline set was implemented. The streamline set is effectively simplified by computing visual effect metric based on iteration. Experimental results show that the visual effects of the streamlines are enhanced on the basis of valid feature-preservation of vector fields.