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We present estimates of stellar age and mass for 0.93 million Galactic diskmain sequence turn-off and sub-giant stars from the LAMOST GalacticSpectroscopic Surveys. The ages and masses are determined by matching withstellar isochrones using Bayesian algorithm, utilizing effective temperature$T_{\rm eff}$, absolute magnitude ${\rm M}_V$, metallicity [Fe/H] and$\alpha$-element to iron abundance ratio [$\alpha$/Fe] deduced from the LAMOSTspectra. Extensive examinations suggest the age and mass estimates are robust.The overall sample stars have a median error of 34 per cent for the ageestimates, and half of the stars older than 2\,Gyr have age uncertainties ofonly 20--30 per cent. Median error for the mass estimates of the whole samplestars is $\sim8$ per cent. The huge dataset demonstrates good correlationsamong stellar age, [Fe/H] ([$\alpha$/H]) and [$\alpha$/Fe]. Particularly,double sequence features are revealed in the both the age--[$\alpha$/Fe] andage--[Fe/H]([$\alpha$/H]) spaces. In the [Fe/H]--[$\alpha$/Fe] space, stars of8--10\,Gyr exhibit both the thin and thick disk sequences, while younger(older) stars show only the thin (thick) disk sequence, indicating that thethin disk became prominent 8--10\,Gyr ago, while the thick disk formed earlierand almost quenched 8\,Gyr ago. Stellar ages exhibit positive vertical andnegative radial gradients across the disk, and the outer disk of$R\gtrsim$\,9\,kpc exhibits a strong flare in stellar age distribution.

Ages and masses of million Galactic disk main sequence turn-off and sub-giant stars from the LAMOST Galactic spectroscopic surveys