We report the discovery of two new unbound hypervelocity stars ( HVSs ) from the LAMOST spectroscopic surveys .
They are respectively a B2V type star of \sim 7 M _ { \odot } with a Galactic rest-frame radial velocity of 502 km s ^ { -1 } at a Galactocentric radius of \sim 21 kpc and a B7V type star of \sim 4 M _ { \odot } with a Galactic rest-frame radial velocity of 408 km s ^ { -1 } at a Galactocentric radius of \sim 30 kpc .
The origins of the two HVSs are not clear given their currently poorly measured proper motions .
However , the future data releases of Gaia should provide proper motion measurements accurate enough to solve this problem .
The ongoing LAMOST spectroscopic surveys are expected to yield more HVSs to form a statistical sample , providing vital constraint on understanding the nature of HVSs and their ejection mechanisms .