  Main sequence turn-off (MSTO) stars have advantages as indicators of Galactic
evolution since their ages could be robustly estimated from atmospheric
parameters. Hundreds of thousands of MSTO stars have been selected from the
LAMOST Galactic sur- vey to study the evolution of the Galaxy, and it is vital
to derive accurate stellar parameters. In this work, we select 150 MSTO star
candidates from the MSTO stars sample of Xiang that have asteroseismic
parameters and determine accurate stellar parameters for these stars combing
the asteroseismic parameters deduced from the Kepler photometry and atmospheric
parameters deduced from the LAMOST spectra.With this sample, we examine the age
deter- mination as well as the contamination rate of the MSTO stars sample. A
comparison of age between this work and Xiang shows a mean difference of 0.53
Gyr (7%) and a dispersion of 2.71 Gyr (28%). The results show that 79 of the
candidates are MSTO stars, while the others are contaminations from either main
sequence or sub-giant stars. The contamination rate for the oldest stars is
much higher than that for the younger stars. The main cause for the high
contamination rate is found to be the relatively large systematic bias in the
LAMOST surface gravity estimates.
