  A sample of the LAMOST spectra of the early type M0-M3 dwarfs is compared
with the Kepler observations. It is found that M dwarfs with strong
chromospheric emission in $H_{\alpha}$ have large flare activity in general.
The rotational periods derived from the Kepler measurements have close
correlations with the sizes of the flares, the power-law distribution index and
the equivalent widths of the $H_{\alpha}$ emission. A clear trend exists for
higher magnetic activities being detected in faster rotating M dwarfs (rotation
periods $<$ 20 day).
