  We report an optical study of transition metal dichalcogenide 2$H$-TaS$_2$
and Na intercalated superconductor Na$_x$TaS$_2$ over a broad frequency range
at various temperatures. A clear gap feature was observed for 2$H$-TaS$_2$ when
it undergoes a CDW transition. The existence of a Drude component in
$\sigma$$_1$($\omega$) below T$_{CDW}$ indicates that the Fermi surface of
2$H$-TaS$_2$ is only partially gapped in CDW state. The spectral evolution of
two different Na$_x$TaS$_2$ crystals further confirms that the partial gap
structure observed in 2$H$-TaS$_2$ has a CDW origin. The CDW mechanism for
2$H$-TaS$_2$, the competition between CDW and superconductivity in
Na$_x$TaS$_2$ system are discussed.
