  Observations of a strong and extended positron-electron annihilation line
emission in the Galactic center (GC) region by the SPI/INTEGRAL are challenging
to the existing models of positron sources in the Galaxy. In this paper, we
study the possibility that pulsar winds from a millisecond pulsar population in
the GC produce the 511 keV line. Our preliminary estimations predict that the
e+/- annihilation rate in the GC is around 5 x 10E+42 sE-1, which is consistent
with the present observational constraints. Therefore, the e+/- pairs from
pulsar winds can contribute significantly to the positron sources in the
Galactic center region. Furthermore, since the diffusion length of positrons is
short in the magnetic field, we predict that the intensity distribution of the
annihilation line should follow the distribution of millisecond pulsars, which
should then correlate to the mass distribution in the GC.
