The present invention relates to a multi-lens monitoring system for bed elevation around a pier according to the present invention comprises a container, a holder, a plurality of photographing units, and a processing module. The container is disposed on the pier; the holder is disposed inside the container; and the plurality of photographing units are disposed on the holder for photographing the bed under water and producing a monitoring image. The processing module is used for activating one of the plurality of photographing units for photographing the bed under water. The processing module also analyzes the monitoring image, gives the elevation variation of the bed, and transmits the elevation variation of the bed to a remote monitoring unit for real-timely monitoring and recording. During the monitoring process, the processing module will change activating one of the plurality of photographing units according to the monitoring image, and hence the electrical power can be saved.