An early warning method for an abnormal state of a lithium battery and a recording medium applicable to a portable electronic device are provided. The method includes the following steps. A plurality of curves of voltage against electric quantity is obtained according to different predicted average current consumptions of the portable electronic device. An operating average current consumption and an operating electric quantity from a first voltage to a second voltage are obtained when the lithium battery at an operating test state in a unit time. One of the curves of voltage against electric quantity is searched, and a warning electric quantity is obtained in a range from the first voltage to the second voltage. The warning electric quantity is compared with the electric quantity, so as to provide an early warning of an abnormal state.