Let N be a nest of projections on a Hilbert space H and J(N) be the corresponding nest algebra. Let A be a large subalgebra of J (N). It is proved that any maximal n-nilpotent ideal of A is in the form of A∩RJ ,where J is a finite subnest of N and RJ is the Jacobson radical of J (J). Using this result can prove that two large subalgebras are isomorphic if and only if the corresponding nests are similar.