  In this paper, we study the circular orbit of the spinning test particle in
the background of a rotating boson star. Using the pole-dipole approximation
and neglecting the back-reaction of the spinning test particle on the
spacetime, the equation of motion of the spinning test particle is described by
the Mathisson-Papapetrou-Dixon equation. We solve this equation under the
Tulczyjew spin-supplementary condition and obtain the four-momentum and
four-velocity of the spinning test particle. Quite different from the spinless
particle, the effective potential of the spinning particle with zero orbital
angular momentum goes to infinite at the center of the rotating boson star.
This will lead to the fact that the spinning particle can not pass through the
center of the boson star. However, when the spin angular momentum and orbital
angular momentum satisfy $2\bar{s}+\bar{l}=0$, the effective potential is not
divergent anymore and the spinning particle can pass through the center of the
rotating boson star. {We still investigate how the spin affects the structure
of the circular orbits and we find that the spin will induce the larger or
smaller regions of no circular orbits, unstable circular orbits, and stable
circular orbits.} Moreover, the radius and energy of the circular orbit will be
decreased or increased by the particle spin. These results will have an
important application in testing the gravitational waves in the boson star
background.
