  The density profile and the clustering of dark matter (DM) halos are two very
important ingredients for understanding many observations of galaxies. In this
talk, I present our new results for these two quantities from a large set of
high quality N-body simulations. We show that in an Einstein de Sitter Universe
about 35 percent of the halos could not be fitted by the Navarro, Frenk & White
(NFW) profile because of too significant substructures, another 50 percent with
less substructures can be reasonably described by the NFW profile, and the rest
with the least substructures can be fitted by the NFW profile very nicely. For
the halos which can be reasonably or better fitted by the NFW profile, the
probability distribution function of the concentration parameter $c$ could be
well described by a lognormal function with a dispersion $\sigma=0.27$. The
mean value of $c$ is quite close to that predicted by NFW, though it decreases
with the increase of the substructures. Our clustering analysis shows a
significantly stronger clustering for low mass halos than Mo & White predict. A
formula is therefore presented for the two-point correlation function of halos
which can fit our simulation results (both CDM models and scale-free clustering
models) very accurately.
