  We apply theoretical spin-down models of magnetospheric evolution and
magnetic field decay to simulate the possible evolution of PSR J0250+5854,
which is the slowest-spinning radio pulsar detected to date. Considering the
alignment of inclination angle in a 3-D magnetosphere, it is possible that PSR
J0250+5854 has a high magnetic field comparable with magnetars or/and high
magnetic field pulsars, if a small inclination angle is considered. Our
calculations show that similar long-period pulsars tend to have a relatively
low period derivative in this case. In another case of magnetic field decay,
calculations also show a possible connection between PSR J0250+5854 and high
dipole-magnetic field magnetars. The evolutionary path indicates a relatively
high spin-down rate for similar long-period pulsars.
