  In order to study the circumnuclear star-forming activity along the Hubble
sequence, we cross-correlate the Sloan Digital Sky Survey Data Release 2 (SDSS
DR2) with the Third Reference Catalog of Bright Galaxies (RC3) to derive a
large sample of 1015 galaxies with both morphological and spectral information.
Among these, 385 sources are classified as star-forming galaxies and the SDSS
fibre covered the circumnuclear regions (0.2 $-$ 2.0 kpc). By using the
spectral synthesis method to remove the contribution from the underlying old
stellar population, we measure the emission lines fluxes accurately which are
then used to estimate the star formation rates(SFRs). Our main findings are
that: (1) Early-type spirals show much larger H$\alpha$ luminosities and hence
higher SFRs, they also suffer more extinctions than late-type ones. The
equivalent widths (EWs) of H$\alpha$ emission lines show the similar trend,
however, the very late types (Sdm $\sim$ Irr) do have large fractions of high
EWs. (2) We confirm that D$_n(4000)$ has strong correlation with the strengthes
of metallic absorption lines (such as CN band, G band and Mg Ib). Both these
lines and the Balmer absorption lines show interesting variations between Sbc
to Sd type galaxies. (3) The bar structure tightly relates with the enhanced
star forming activity, this effect is even more significant in the early-type
spirals. But we should note that the bar structure is not a necessary or
sufficient condition for galaxies to harbor circumnuclear star formations.
