Abstract: The present invention relates to a lithium secondary battery with a built-in protective circuit, which includes battery case (1), a battery core (2) and electrolyte. According to the present invention, a built-in protective circuit module (4) is provided to act as the connection between terminals of positive and negative electrodes (21 and 22) and output ends of positive and negative electrodes (31 and 32) inside the battery. The battery of the present invention has the advantages of safe and reliable protection against short-circuit, over-charge, over-discharge and over-current in the application, and therefore it is reliable power supply for the portable electronic appliances such as mobile phones and the like.