A crane monitoring system includes a first detection apparatus, a processing apparatus and a second detection apparatus. The first detection apparatus is configured to detect a position of a crane, to send a first detection signal when the crane is located above a Front Opening Unified Pod (FOUP) load port of a semiconductor processing device, and to send a second detection signal when the crane leaves a space above the FOUP load port. The processing apparatus is configured to generate a start control signal responsive to receiving the first detection signal, and to generate a stop control signal responsive to receiving the second detection signal. The second detection apparatus is configured to start a detection of whether there is a foreign matter between the crane and the FOUP load port after receiving the start control signal, and to stop the detection after receiving the stop control signal.