The total-energy change is systematically evaluated in this paper when the thin ZrO2(T) ellipsoidal plate at different orientation transforms into ZrO2(M) under extension, compression and shear stresses. The optimal orientation of Martensitic uncleation is determined by using the oriterion of minimum energy. The numerical results show that the shear strains resulting from the transformation affect obviously the orientation of Martensitic nucleation and the critical stresses inducing transformation are very different.