  We present the observed H$\alpha$ flux and derived star formation rates
(SFRs) for a fall sample of low$-$surface$-$brightness galaxies (LSBGs). The
sample is selected from the fall sky region of the 40$\%$ ALFALFA {\ion{H}{1}}
survey $-$ SDSS DR7 photometric data, and all the $H\alpha$ images were
obtained using the 2.16 m telescope, operated by the National Astronomy
Observatories, Chinese Academy of Sciences. A total of 111 LSBGs were observed
and $H\alpha$ flux was measured in 92 of them. Though almost all the LSBGs in
our sample are {\ion{H}{1}}$-$rich, their SFRs derived from the extinction and
filter$-$transmission$-$corrected $H\alpha$ flux, are less than
1$M_{\sun}$$yr^{-1}$.
  LSBGs and star forming galaxies have similar {\ion{H}{1}} surface densities,
but LSBGs have much lower SFRs and SFR surface densities than star$-$forming
galaxies. Our results show that LSBGs deviate from the Kennicutt-Schmidt law
significantly, which indicate that they have low star formation efficiency. The
SFRs of LSBGs are close to average SFRs in Hubble time and support the previous
arguments that most of the LSBGs are stable systems and they tend to seldom
contain strong interactions or major mergers during their star formation
histories.
