  The diffuse gamma-rays in the Galactic center region have been studied. We
propose that there exists a population of millisecond pulsars (MSPs) in the
Galactic Center, which will emit GeV gamma-rays through the
synchrotron-curvature radiation as predicted by outer gap models. These GeV
gamma-rays from unresolved millisecond pulsars probably contribute to the
diffuse gamma-ray spectrum detected by EGRET which displays a break at a few
GeV. We have used the Monte Carlo method to obtain the simulated samples of
millisecond pulsars in the Galactic center region covered by EGRET ($\sim
1.5^\circ$) according to the different period and magnetic field distributions
from the observed millisecond pulsars in the Galactic field and globular
clusters, and superposed their synchrotron-curvature spectra to derive the
total GeV flux. Our simulated results suggest that there probably exist about
6000 unresolved millisecond pulsars in the region of the angular resolution for
EGRET, whose emissions could contribute significantly to the observed diffuse
gamma-rays in the Galactic center.
