An operation method to operate a tilt sensor with power-saving mechanism is provided. The operation method comprises the steps as follows. An accommodating space is provided such that a blocking object is displaceable in the accommodating space according to the gravity. A working mode is performed such that a light-emitting element emits light according to a first current and at least two first light sensors sense a light amount to determine a tilt angle of the tilt sensor. When the light amount doesn't change or when a light amount variation sensed by a second light sensor is smaller than the threshold value within a predetermined time period, a power-saving mode is performed such that the light-emitting element emits light according to a second current smaller than the first current. When the light amount variation is larger than the specific value during the power-saving mode, the working mode is performed.