Slotted blade tip is an newly developed design to reduce the strength of tip vortex. In numerical simulation, vortex strength is likely to suffer from unreasonable mesh distribution and computational method because of its highly concentrated structure, which leads to premature dissipation of vortexs, and makes it hard to track the wake vortex development. To the question, special techniques are adopted in the simulation including local refinement of overlap grids and rotation correction of turbulence model, and high resolution tip vortex flowfields are obtained. Thereafter, the hovering flowfields of Caradonna-Tung rotors equipped with original and slotted tip are numerically simulated, vorticity contours and characteristic velocities are discussed to study the flow mechanism, and four slotted blade tips are compared for their control efficiencies and performance losses. Results show that slotted blade tips reduce the strength of the blade tip vortex effectively, and at the same time, some minus effects are induced such as thrust loss and torque addition.