We study the metallicity distribution and kinematic properties of 4,680 A/F/G/K-type giant stars with |z| > 5 kpc selected from the LAMOST spectroscopic survey .
The metallicity distribution of giant stars with 5 < |z| \leqslant 15 kpc can be described by a three-peak Gaussian model with peaks at [ Fe/H ] \sim - 0.6 \pm 0.1 , -1.2 \pm 0.3 and -2.0 \pm 0.2 , corresponding to the ratio of 19 \% , 74 \% and 7 \% , respectively .
The [ \alpha / Fe ] is used to associate the three peaks with the thick disk , inner-halo and outer-halo components of the Galaxy .
The metallicity distribution of these giant stars , which is fit with Gaussians corresponding to the three components , show a growing fraction of inner-halo component and declining fraction of the thick-disk component with increasing distance from the Galactic plane .
Adopting a galaxy potential model , we also derive the orbital parameters of the sample stars , such as orbit eccentricity and rotation velocity .
The peak values of derived orbital eccentricity for stars covering different metallicity regions maintain e \sim 0.75 , independent of height above the plane , within the range 5 < |z| < 15 kpc .
By comparing the MDFs of stars in different rotation velocity intervals , we find that the majority of the retrograde stars are more metal-poor than the prograde stars .