Abstract: A negative electrode of a thin film battery and method for forming the same, wherein the negative electrode comprises a porous structural layer, a capacitor layer, and a lithium ion source layer. The porous structural layer is formed on a metal substrate, and a thickness of the porous structural layer is between 200 nm and 700 nm. The capacitor layer is formed on the porous structural layer, and a thickness is between 100 nm and 300 nm. The lithium ion source layer is formed on the capacitor layer. Since the porous structural layer is made of stable material, a problem of charging-discharging instability that is occurred due to damage of battery structure caused by the volume expansion of the capacitor layer during the charging-discharging process can be improved. In addition, the negative electrode can be combined with a positive electrode for forming a thin film battery.