This paper discusses the magnetic drag force resulting from the relative motion of a permanent magnet moving along a finite dimensional conducting plate. The image method with imaginary eddy currents is investigated. Boundary conditions are established to ensure that the eddy currents vanished at the boundaries of the conducting plate. Magnetic drag force is computed based on the eddy current distributions using Lorentz force law. A test system is built to demonstrate the magnetic brakes arose from the electromagnetic interactions.