  We use the LAMOST spectra of member stars in Pleiades, M34, Praesepe, and
Hyades to study how chromospheric activity vary as a function of mass and
rotation at different age. We measured excess equivalent widths of H$\alpha$,
H$\beta$, and Ca~{\sc ii} K based on estimated chromospheric contributions from
old and inactive field dwarfs, and excess luminosities are obtained by
normalizing bolometric luminosity, for more than 700 late-type stars in these
open clusters. Results indicate two activity sequences in cool spot coverage
and H$\alpha$ excess emission among GK dwarfs in Pleiades and M dwarfs in
Praesepe and Hyades, paralleling with well known rotation sequences. A weak
dependence of chromospheric emission on rotation exists among ultra fast
rotators in saturated regime with Rossby number Ro$\lesssim0.1$. In the
unsaturated regime, chromospheric and coronal emission show similar dependence
on Ro, but with a shift toward larger Ro, indicating chromospheric emission
gets easily saturated than coronal emission, and/or convective turnover
time-scales based on X-ray data do not work well with chromospheric emission.
More interestingly, our analysis show fully convective slow rotators obey the
rotation-chromospheric activity relation similar to hotter stars, confirming
the previous finding. We found correlations among H$\alpha$, H$\beta$, and
Ca~{\sc ii} K emissions, in which H$\alpha$ losses are more important than
Ca~{\sc ii} K for cooler and more active stars. In addition, a weak correlation
is seen between chromospheric emission and photospheric activity that shows
dependency on stellar spectral type and activity level, which provides some
clues on how spot configuration vary as a function of mass and activity level.
