  The recently observed bright optical transients(OT) of high redshift GRBs
indicate that they are in a violent dynamical state. We think it is reasonable
to assume that the GRBs form in the environment of gravitationally collapsed
halos of the cosmic matter field, and we investigate the basic parameters of
the halos which are favored to host GRBs. If the harboring coefficient $f$ of
GRBs per halo is weakly dependent on the mass of the halo, the redshift data of
GRB OTs can yield significant constraints on the massive halos hosting GRBs. We
show that, in the framework of popular cold dark matter (CDM) models, the
GRB-favored environments are newly collapsed halos (i.e. their ages less than
about $2 \times 10^9$ yr) with masses around $10^9$ $h^{-1}$ M$_{\odot}$. In
this scenario, low redshift GRBs, if they exist, could not have the same cosmic
origin as the high redshift ones. To fit with the observed rate of GRBs, we
conclude that each GRB halo can host probably no more than one GRB event on
average. This result implies that GRBs may be related to the merging of the
halos.
