Let G be a finite group and σ = {σ
i
| i ∈ I} some partition of the set of all primes
$\Bbb{P}$
. Then G is said to be: σ-primary if G is a σ
i
-group for some i; σ-nilpotent if G = G1× … × G
t
for some σ-primary groups G1, … , G
t
; σ-soluble if every chief factor of G is σ-primary. We use
$G^{{\mathfrak{N}}_{\sigma}}$
to denote the σ-nilpotent residual of G, that is, the intersection of all normal subgroups N of G with σ-nilpotent quotient G/N. If G is σ-soluble, then the σ-nilpotent length (denoted by l
σ
(G)) of G is the length of the shortest normal chain of G with σ-nilpotent factors. Let N
σ
(G) be the intersection of the normalizers of the σ-nilpotent residuals of all subgroups of G, that is,
$${N_\sigma }(G) = \bigcap\limits_{H \le G} {{N_G}} ({H^{{_\sigma }}}).$$
Then the subgroup N
σ
(G) is called the σ-nilpotent norm of G. We study the relationship of the σ-nilpotent length with the σ-nilpotent norm of G. In particular, we prove that the σ-nilpotent length of a σ-soluble group G is at most r (r > 1) if and only if l
σ
(G/ N
σ
(G)) ≤ r.