AlN can be employed in mechanical sensors1-3 because of its good piezoelectric properties.In this work,we discussed the effect of uniaxial and biaxial mechanical pressure on the the longitudinal elastic constant(C33),piezoelectric constant(e33),static dielectric constant(ε33),mass density(ρ)and the longitudinal acoustic wave velocity(V,which is defined by C33,e33,ε33 and ρ)of AlN based on first-principle calculations.The results shown that the pressure along c axis of AlN unit cell will increase e33 and decrease C33 while that in the basal plane has the opposite effect.All the pressures will decrease ε33 and increase ρ of AlN.The results show that the pressure in the basal plane has significant effect on V of AlN while the effect of pressure along c axis on V are not obvious.The pressure-introduced variation of C33,e33 and ρ have significant effect on V while that of ε33 has little effect on V so that it can be ignored in the calculation of V.Those works provide a possible way to predict the performance of piezoelectric mechanical sensors based on the intrinsic properties of piezoelectric materials4-5.