AbstractIn this paper, we will use the convex modular $$\rho ^{*}(f)$$
ρ
∗
(
f
)
to investigate $$\Vert f\Vert _{\Psi ,q}^{*}$$
‖
f
‖
Ψ
,
q
∗
on $$(L_{\Phi })^{*}$$
(
L
Φ
)
∗
defined by the formula $$\Vert f\Vert _{\Psi ,q}^{*}=\inf _{k>0}\frac{1}{k}s_{q}(\rho ^{*}(kf))$$
‖
f
‖
Ψ
,
q
∗
=
inf
k
>
0
1
k
s
q
(
ρ
∗
(
k
f
)
)
, which is the norm formula in Orlicz dual spaces equipped with p-Amemiya norm. The attainable points of dual norm $$\Vert f\Vert _{\Psi ,q}^{*}$$
‖
f
‖
Ψ
,
q
∗
are discussed, the interval for dual norm $$\Vert f\Vert _{\Psi ,q}^{*}$$
‖
f
‖
Ψ
,
q
∗
attainability is described. By presenting the explicit form of supporting functional, we get sufficient and necessary conditions for smooth points. As a result, criteria for smoothness of $$L_{\Phi ,p}~(1\le p\le \infty )$$
L
Φ
,
p
(
1
≤
p
≤
∞
)
is also obtained. The obtained results unify, complete and extended as well the results presented by a number of paper devoted to studying the smoothness of Orlicz spaces endowed with the Luxemburg norm and the Orlicz norm separately.