Using a nonadiabatic evolution method, we investigate the spin-nip process ofpolaron in polymers with a magnetic impurity. Our results show that when the spin orientation of this impurity is fixed to be perpendicular to the spin ofpolaron (θ=π/2), the magnetic impurity causes a spin-flip process. The probability of the spin-Sip increases with the increase of exchange integral J up to about 0.35 eV and then decreases with the increase of J. In the case J is fixed while the spin orientation is adjustable, we find the probability of the spin-flip varies with the impurity orientation and reaches a maximum value at θ=π/2.