  We present and analyze the possibility of using optical ${\it u}$-band
luminosities to estimate star-formation rates (SFRs) of galaxies based on the
data from the South Galactic Cap ${\it u }$ band Sky Survey (SCUSS), which
provides a deep ${\it u}$-band photometric survey covering about 5000 $deg^2$
of the South Galactic Cap. Based on two samples of normal star-forming galaxies
selected by the BPT diagram, we explore the correlations between ${\it
u}$-band, H$\alpha$, and IR luminosities by combing SCUSS data with the Sloan
Digital Sky Survey (SDSS) and ${\it Wide}$-${\it field\ Infrared\ Survey\
Explorer}$ (${\it WISE}$). The attenuation-corrected ${\it u}$-band
luminosities are tightly correlated with the Balmer decrement-corrected
H$\alpha$ luminosities with an rms scatter of $\sim$ 0.17 dex. The IR-corrected
${\it u }$ luminosities are derived based on the correlations between the
attenuation of ${\it u}$-band luminosities and ${\it WISE}$ 12 (or 22) $\mu$m
luminosities, and then calibrated with the Balmer-corrected H$\alpha$
luminosities. The systematic residuals of these calibrations are tested against
the physical properties over the ranges covered by our sample objects. We find
that the best-fitting nonlinear relations are better than the linear ones and
recommended to be applied in the measurement of SFRs. The systematic deviations
mainly come from the pollution of old stellar population and the effect of dust
extinction; therefore, a more detailed analysis is needed in the future work.
