Pressure-dependent phase transition of zirconia has attracted great interest due to its applications in high temperature and high pressure environments. In this paper, an a ab initio model was developed to study the phase transition in high pressures. Hydrostatic compressive pressures from 0 to 80 GPa were applied to an unit cell of monociinic phase zirconia, and the lattice structure change was measured. The simulations correctly predict the phase transitions of m-ZrO2 under compressive pressures ranging from 0 to 70 GPa. The phase transition pressure of monociinic to orthorhombic with the space group of Phcm is at about 20 GPa. When further compression is applied till 40 GPa, zirconia transforms from orthorhombic to tetragonal. This tetragonal phase is stable from 40 GPa to 60 GPa.