The utility model provides a self-powered fire alarm, and relates to the technical field of alarms. The self-powered fire alarm comprises a buzzer and a power supply device, and the power supply device is suitable for converting external impact into electric energy and transmitting the electric energy to a storage battery to be stored for the buzzer to work; the power supply device comprises a sliding shell and a rotating shell, the rotating shell comprises a first hollow cavity, and the sliding shell is suitable for being inserted into the first hollow cavity to move up and down; the slidingshell comprises a second hollow cavity, and the first hollow cavity and the second hollow cavity are coaxial to form a damping cavity; a piezoelectric transduction device is arranged on the rotating shell, and the piezoelectric transduction device is made of piezoelectric materials. According to the self-powered fire alarm, uncontrollable strong-impact mechanical energy is converted into controllable mechanical energy through the power supply device, the ram impacts the piezoelectric structure to convert the mechanical energy into electric energy, an extra power supply is provided for equipment, and energy conservation is facilitated.