  In this paper, we introduce the Carleson measure spaces with variable
exponents $CMO^{p(\cdot)}$. By using discrete Littlewood$-$Paley$-$Stein
analysis as well as Frazier and Jawerth's $\varphi-$transform in the variable
exponent settings, we show that the dual space of the variable Hardy space
$H^{p(\cdot)}$ is $CMO^{p(\cdot)}$. As applications, we obtain that Carleson
measure spaces with variable exponents $CMO^{p(\cdot)}$, Campanato space with
variable exponent $\mathfrak{L}_{q,p(\cdot),d}$ and H\"older-Zygmund spaces
with variable exponents $\mathcal {\dot{H}}_d^{p(\cdot)}$ coincide as sets and
the corresponding norms are equivalent. Via using an argument of weak density
property, we also prove the boundedness of Calder\'{o}n-Zygmund singular
integral operator acting on $CMO^{p(\cdot)}$.
