A detection-alarm mechanism is provided. The detection-alarm mechanism for a tire includes a sensor, an electronic processing unit, a post-processing unit and a display unit. The sensor includes a substrate disposed in the tire and at least one photoelectronic element fixed to the substrate. If the tire is cracked, light passes through the cracks and reaches the photoelectronic elements to generate signals. The electronic processing unit receives signals from the photoelectronic elements to generate wear information. The post-processing unit is disposed in a vehicle on which the tire is installed and receives wear information from the electronic processing unit. The display unit is disposed in the vehicle for presenting the wear information.