The invention discloses a method for improving the bonding strength of a ruthenium oxide coating and a tantalum substrate, and belongs to a preparation method for a capacitor electrode. According to the method, valve metal powder is added into ruthenium-compound-containing slurry which is coated on the surface of the tantalum substrate, and then the dried tantalum substrate is subjected to thermal decomposition in a water-vapor environment to form an amorphous ruthenium dioxide hydrate cathode, so the dehydration and the crystallization of the ruthenium dioxide can be avoided; therefore, the bonding strength of ruthenium oxide and the tantalum substrate is improved. The capacitor electrode prepared by the method has the advantages of high high-temperature resistance, high vibration resistance and the like; and by the method, the reliability of a capacitor is improved.