The present invention provides a sound generation device and a preparation method of a metal plastic part. The sound generation device comprises a metal plastic part. The metal plastic part comprises a plastic part and a metal insert that is combined with the plastic part. An oxidation film that is obtained through metal nanocrystallization and a nanopore that is formed in a surface of the oxidation film and has a pore diameter of 20-1,000 nm are arranged on a surface of the metal insert. The nanopore is filled with a resin composition from which the plastic part is made. As the nanopore is filled with the resin composition from which the plastic part is made, the metal insert and the plastic part are in close fit with each other, which greatly enhances the gluing capability of the metal insert and prevents the metal insert and the plastic part which are formed through injection molding from being separated. A length of a portion embedded into the plastic part of the metal insert is greatly reduced, such that transfer of ultrasonic energy is smooth. The metal plastic part is effectively prevented from ultrasonic unmelting. Thus, the waterproofness and the sealing property of the metal plastic part are improved. Accordingly, the performance of the sound generation device is improved.