  According to the observational limits on the radius and mass, the fastest
rotating pulsar (PSR 1937+21) is probably a strange star, or at least some
neutron star equations of state should be ruled out, if we suggest that a
dipole magnetic field is relevant to its radio emission. We presume that the
millisecond pulsar is a strange star with {\em much} low mass, small radius,
and weak magnetic moment.
