The invention discloses a method for preparing a thermal barrier coating. According to the method disclosed by the invention, a deposition matrix is bombarded by ion beams while a deposition coating is evaporated by electron beams, the steam energy of the electron beams is about 0.1-1 electron volts, and the energy is not enough to well migrate atoms in the process of depositing the coating; and the energy of the ion beams can reach thousands of electron volts, and the energy is enough to interfere growth of columnar crystals to increase crystal boundaries and crystal sub-boundaries and enlarge or increase microscopic holes so as to reduce phonon and photon scattering mean free path and reduce the thermal conductivity of the thermal barrier coating. The energy of vaporous clouds can be increased through activation ionization effects of ions; and compared with the conventional EB-PVD (Electron Beam Physical Vapour Deposition), the method can ensure that same performances can be achieved at low deposition temperature; furthermore, forms, structures and stresses of the columnar crystals can be also adjusted and controlled through ion assisted deposition, and thus, the service life ofthe thermal barrier coating can be prolonged.