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We present the observed H$\alpha$ flux and derived star formation rates(SFRs) for a fall sample of low$-$surface$-$brightness galaxies (LSBGs). Thesample 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 wereobtained using the 2.16 m telescope, operated by the National AstronomyObservatories, Chinese Academy of Sciences. A total of 111 LSBGs were observedand $H\alpha$ flux was measured in 92 of them. Though almost all the LSBGs inour sample are {\ion{H}{1}}$-$rich, their SFRs derived from the extinction andfilter$-$transmission$-$corrected $H\alpha$ flux, are less than1$M_{\sun}$$yr^{-1}$.  LSBGs and star forming galaxies have similar {\ion{H}{1}} surface densities,but LSBGs have much lower SFRs and SFR surface densities than star$-$forminggalaxies. Our results show that LSBGs deviate from the Kennicutt-Schmidt lawsignificantly, which indicate that they have low star formation efficiency. TheSFRs of LSBGs are close to average SFRs in Hubble time and support the previousarguments that most of the LSBGs are stable systems and they tend to seldomcontain strong interactions or major mergers during their star formationhistories.

An H$\alpha$ Imaging Survey of the Low-surface-brightness Galaxies Selected from the Fall Sky Region of the 40$\%$ ALFALFA \ion{H}{1} Survey