An over-power protection apparatus for self-excited power converter comprises a soft-start unit, an adjusting unit and a timing unit. A PWM unit of the self-excited power converter generates a switching signal in response to a compensating signal of the soft-start unit to control the output power of the self-excited power converter. The soft-start unit couples to the adjusting unit. The adjusting unit drives the soft-start unit and the PWM unit for modulating the switching signal to reduce the pulse width of the switching signal and the output power of the self-excited power converter once the short-circuit and over-load are happened at the output of the self-excited power converter. In the meantime, a timing unit starts to count. The timing unit drives the self-excited power converter to stop supplying the power source after the counting and the over-power lasting for a period of time.