  We study the differential energy distribution of dark matter halos, carrying
out cosmological N-body simulation.We give an analytical formula of the
differential energy distribution of dark matter in the halos obtained by the
numerical simulation.From the analytical formula we reconstruct the density
profile described by the Navarro,Frenk, & White (NFW) profile.The NFW profile
is consistent with the analytical formula of our fractional mass distribution.
We find that a parameter in our analytical formula of differential energy
distribution which is related with the slope of inner cusp of dark halo.We
obtain the distribution function for the NFW profile which has sharp cut off at
the high binding energy.We discuss physical reason of form of the analytical
formula.
