Let
R
0
=
G
R
p
k
r
,
p
k
be a Galois maximal subring of
R
so that
R
=
R
0
⊕
U
⊕
V
⊕
W
⊕
Y
, where
U
,
V
,
W
, and
Y
are
R
0
/
p
R
0
spaces considered as
R
0
-modules, generated by the sets
u
1
,
⋯
,
u
e
,
v
1
,
⋯
,
v
f
,
w
1
,
⋯
,
w
g
, and
y
1
,
⋯
,
y
h
, respectively. Then,
R
is a completely primary finite ring with a Jacobson radical
Z
R
such that
Z
R
5
=
0
and
Z
R
4
≠
0
. The residue field
R
/
Z
R
is a finite field
G
F
p
r
for some prime
p
and positive integer
r
. The characteristic of
R
is
p
k
, where
k
is an integer such that
1
≤
k
≤
5
. In this paper, we study the structures of the unit groups of a commutative completely primary finite ring
R
with
p
ψ
u
i
=
0
,
ψ
=
2
,
3
,
4
;
p
ζ
v
j
=
0
,
ζ
=
2
,
3
;
p
w
k
=
0
, and
p
y
l
=
0
;
1
≤
i
≤
e
,
1
≤
j
≤
f
,
1
≤
k
≤
g
, and
1
≤
l
≤
h
.