AbstractThe spatial structure of the Milky Way outer disk is characterized with ~ 70000 LAMOST DR3 K giants after carefully correction of their selection effects. By slicing the data into various Galactocentric radius bins, we are able to fit the vertical stellar density profile with a models composed of two isothermal-sheet disks and an oblate power-law halo. We find that although the thin disk is significantly flared, the radial surface density profile can extend to as far as 19 kpc. Beyond 12 kpc, only one thicker disk, rather than two disk components, are found in the samples. Moreover, the residual of the density profiles after subtracting the best fit models show different oscillation patterns in almost all range of detecting radius.