Abstract: An earthquake warning system includes an acceleration detection unit, a controller unit and an alarming unit. The acceleration detection unit is for detecting a plurality of earthquake accelerations respectively with respect to a plurality of axes, and generates a plurality of detecting signals. The controller unit is electrically connected to the acceleration detection unit for receiving the detecting signals therefrom, and generates a detection value. The alarming unit is operable under a plurality of alarming modes which respectively correspond to the seismic scales and in each of which an alarm having a distinct alarming level that corresponds to the corresponding one of the seismic scales is produced.