  In this paper we investigate the innermost stable circular orbit (ISCO) for a
classical spinning test particle in the background of Kerr-Newman black hole.
It is shown that the orbit of the spinning particle is related to the spin of
the test particle. The motion of the spinning test particle will be
superluminal if its spin is too large. We give an additional condition by
considering the superluminal constraint for the ISCO in the black hole
backgrounds. We obtain numerically the relations between the ISCO and the
properties of the black holes and the test particle. It is found that the
radius of the ISCO for a spinning test particle is smaller than that of a
non-spinning test particle in the black hole backgrounds.
