  We study the density structures of dark matter subhalos for both cold dark
matter and self-interacting dark matter models using high-resolution
cosmological $N$-body simulations. We quantify subhalo's central density at 150
pc from the center of each subhalo at the classical dwarf spheroidal and
ultrafaint dwarf scales found in Milky-Way sized halos. By comparing them with
observations, we find that the self-interacting scattering cross-section of
$\sigma/m<3\ \rm{cm^{2}g^{-1}}$ is favored. Due to the combination of hosts'
tide and self-interactions, the central density of subhalos with small
pericenter shows a noticeable difference between the cold and the
self-interacting models, indicating that Milky-Way satellites with small
pericenter are ideal sites to further constrain the nature of dark matter by
future large spectroscopic surveys.
