  We download the LAMOST DR8 low resolution catalog 6,478,063 AFGK tpye stars
and plot the figures of effective temperature, gravitational acceleration, and
metal abundance. Some small and medium mass stars are evolved from pre-main
sequence or main sequence stage to planetary nebula stage or white dwarf stage
by the stellar evolution code \texttt{MESA}. We analyze the observed
statistical data and model calculation results, and then obtain some basic
conclusions preliminarily. Most red giant and asymptotic giant stars with
log$g$ less than 0.85 have poor metal abundance. Most hot A type main-sequence
stars are metal rich stars with log$g$ from 3.5 to 4.5. The conclusions are
reasonable within a certain error range. The theory of a gap area in the H-R
diagram for stellar evolutions of medium mass stars is reflected in the
statistical figures. The central core hydrogen burning stage and the central
core helium burning stage correspond to the peak structures in the
gravitational acceleration statistical figures respectively. The metal
abundances among A, F, G, and K type stars have a wide distribution. We can not
simply replace the metal abundances of these stars with the metal abundance of
the Sun when doing a fine research work.
