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We determined the chemical and kinematic properties of the Galactic thin andthick disk using a sample of 307,246 A/F/G/K-type giant stars from the LAMOSTspectroscopic survey and Gaia DR2 survey. Our study found that the thick diskglobally exhibits no metallicity radial gradient, but the inner disk ($R \le 8$kpc) and the outer disk ($R>8$ kpc) have different gradients when they arestudied separately. The thin disk also shows two different metallicity radialgradients for the inner disk and the outer disk, and has steep metallicityvertical gradient of d[Fe/H]/d$|z|$ $=-0.12\pm0.0007$ dex kpc$^{-1}$, but itbecomes flat when it is measured at increasing radial distance, while themetallicity radial gradient becomes weaker with increasing vertical distance.Adopting a galaxy potential model, we derived the orbital eccentricity ofsample stars and found a downtrend of average eccentricity with increasingmetallicity for the thick disk. The variation of the rotation velocity with themetallicity shows a positive gradient for the thick disk stars and a negativeone for the thin disk stars. Comparisons of our observed results with models ofdisk formation suggest that radial migration could have influenced the chemicalevolution of the thin disk. The formation of the thick disk could be affectedby more than one processes: the accretion model could play an indispensablerole, while other formation mechanisms, such as the radial migration or heatingscenario model could also have a contribution.

Chemical and Kinematic Properties of the Galactic Disk from the LAMOST and Gaia Sample Stars