The invention provides a method for producing an integrally formed silicon-based balance spring with a final-coil balance spring part for regulating a mechanical clock. The method comprises the following steps of providing the silicon-based balance spring, wherein the silicon-based balance spring is provided with a main body part and an outer part for forming the final-coil balance spring part, the outer part radially extends outwards from the outermost turn of the main body part, and the main body part and the outer part are integrally formed from a silicon-based material in a coplanar configuration way; moving the outer part in a direction opposite to and away from the plane of the main body part and a direction passing through the main body part and facing the plane of the main body part; providing a stress relaxation process for the balance spring to reduce internal stress induced in the balance spring, wherein the outer part is configured and positioned by the final-coil balance spring part relative to the main body part after moving into the plane of the main body part.