  It is shown that all string fields except dilaton are non-propagating in the
(2+1)-dimensional black string. One finds that the perturbation around the
black string reveals a mixing between the dilaton and other fields. Under the
new gauge(dilaton gauge), we disentangle this mixing and obtain one decoupled
dilaton equation. It turns out that this black string is stable. From the
scattering of dilaton off the neutral black string(N=0), we find the absorption
cross-section. Further the absorption cross-section for minimally coupled
scalar is obtained and we compared it with that of dilaton.
