The spark plug is an important factor in the ignition system of a gasoline engine. It introduces high-voltage electricity into the combustion chamber, jumps across the gap between electrodes to generate sparks, and ignites the combustible mixture in the cylinder. It mainly consists of lead nuts, insulators, lead screws, center electrodes, and side electrodes. It is composed of a shell and a side electrode, and the side electrodes are welded to the shell.