To effectively monitor marine disaster-inducing organisms, such as Jellyfish and Acetes, at nuclear power plant intakes, an acoustic detection method utilizing broadband sonar is employed. This approach enables the capture of their echo characteristics, the analysis of their distribution density and biomass in sensitive marine areas, and the efficient monitoring of organism numbers, and the identification of biological species. In this study, a marine biohazard monitoring and early warning system was designed to provide real-time surveillance of the distribution intensity of biohazard organisms in sensitive marine zones. The system is equipped to trigger an alarm when predefined thresholds are exceeded, thereby facilitating prompt manual intervention. The monitoring and early warning system has undergone rigorous sea trials to validate its efficacy. The results underscore the effectiveness of this acoustic-based marine biological monitoring and early warning system in tracking marine disaster organisms at nuclear power plant intakes. It not only delivers real-time monitoring data but also offers timely warnings, demonstrating its substantial practical value. [Chinese Fishery Quality and Standards, 2024, 14(4): 36-44]