The two sides of the metal flat gasket are machined into concentric 90-degree angle wave-shaped serrated grooves with a precision lathe or a special milling machine. Due to the contact with other sealing surfaces being multiple concentric circle line contacts, it has a labyrinth seal effect. According to different media and working conditions, flexible graphite, PTFE, asbestos-free board or other soft materials can be pasted on both sides of the gasket. By taking advantage of the sealing property of the soft covering layer and the strength and elasticity of the metal, a better sealing effect can be achieved.