The different influence of aging on dependence of the Relaxation processes and Acoustic Emission registrated under microindentation of MgO single crystals subjected to axial compression from indentor value load has been revealed. The AE intensity after aging during 2400 hours is increased at small load, on the contrary, decreased at large one. The Relaxation coefficient is markedly decreased after aging and value of such effect is depended on the preliminary deformation degree. Magnitude of microhardness after long-term aging is increased but slightly (10−15%). However, its maximal increase after little time is observed. It was shown that the acoustic emission and relation effects observed after aging are probably related to the existence of different distribution of stresses into the subsurface layers of the MgO deformed. In this case the sign and magnitude of stress are changed against the depth of layer and ascertain the modification of parameters investigated after aging.