  It is well known that some black holes can act as accelerators for particles
without spin. Recently, there are some works considering collision of two
spinning particles in the background of Schwarzschild and Kerr black holes and
it was shown that {the center-of-mass energy of the test particles is related
to the spin}. In this paper we extend the results to some more general cases.
We consider Kerr-Newman black holes as accelerators for spinning particles. We
derive the center-of-mass energy of the spinning particles and use numerical
method to investigate how the center-of-mass energy is affected by the
properties of the black holes and spinning particles.
