  We perform numerical simulations to study the Habitable zones (HZs) and
dynamical structure for Earth-mass planets in multiple planetary systems. For
example, in the HD 69830 system, we extensively explore the planetary
configuration of three Neptune-mass companions with one massive terrestrial
planet residing in 0.07 AU $\leq a \leq$ 1.20 AU, to examine the asteroid
structure in this system. We underline that there are stable zones of at least
$10^5$ yr for low-mass terrestrial planets locating between 0.3 and 0.5 AU, and
0.8 and 1.2 AU with final eccentricities of $e < 0.20$. Moreover, we also find
that the accumulation or depletion of the asteroid belt are also shaped by
orbital resonances of the outer planets, for example, the asteroidal gaps at
2:1 and 3:2 mean motion resonances (MMRs) with Planet C, and 5:2 and 1:2 MMRs
with Planet D. In a dynamical sense, the proper candidate regions for the
existence of the potential terrestrial planets or HZs are 0.35 AU $< a < $ 0.50
AU, and 0.80 AU $< a < $ 1.00 AU for relatively low eccentricities, which makes
sense to have the possible asteroidal structure in this system.
