A tilt sensor with power-saving mechanism is provided. The tilt sensor includes a light-emitting element, a blocking object displaceable in an accommodating space on a baseboard, at least two first light sensors, a second light sensor and a control module. The first and the second light sensors respectively sense a light amount and a light amount variation according to the relative position of the light-emitting element and the blocking object. During a power-saving mode, when the light amount variation is larger than a specific value, the control module makes the light-emitting element work in a working mode to emit light according to a first current. During the work mode, when the light amount does not change or the light amount variation is smaller than a threshold value, the control module makes the light-emitting element work in the power-saving mode to emit light according to a second current.