The invention discloses a masonry beam deformation monitoring system and monitoring and forewarning method based on a Hopfield neural network. The masonry beam deformation monitoring system comprisesa grating optical fiber sensor arranged at each monitoring point in a roadway and an optical fiber grating demodulator arranged on a well and in communication connection with the grating optical fibersensors through a downhole monitoring system platform. The signal output end of the optical fiber grating demodulator is connected with a Hopfield neural network processing system, and the Hopfield neural network processing system and a storage searching server conduct information interaction. By adopting the masonry beam deformation monitoring system and monitoring and forewarning method, multi-point and multi-parameter monitoring is achieved; the grating optical fiber sensor are assembled to collect data, mining optical fibers are adopted for transmission, so that the capability of resisting electromagnetic interference is high, and operation is stable; and the data are processed based on the Hopfield neural network processing system, and a data platform is shared, so that parameters can be optimized, the forewarning and alarming threshold value can be further adjusted according to the deformation situation of the downhole roadway, and thus the efficacy of the monitoring system is improved greatly.