  A possible relation between the high dispersion in metallicity of metal-poor
halo stars and the minor merger processes in the history of the Galaxy is
presented. The foreign populations of stars in the satellites through minor
merger processes, make considerable contributions to the Galactic halo,
therefore alter the intrinsic distribution of metallicities of the halo stars.
Our model reproduces the observed trends in the metallicity distribution of the
extremely metal-poor halo field stars in the Galaxy. Taken all the parameters
for our model, a density of $1.9\times 10^{-3}kpc^{-3}$ of extremely metal-poor
halo stars in $-5<[Fe/H]<-4$ is predicted, which explains why no such stars
have been observed so far.
