Abstract: [Purposes] Single beam unmanned vessels serve as critical tools for water depth measurement and underwater topographic mapping.To address the challenges of incomplete data acquisition and the risk of hull grounding during nearshore operations，this study proposes a measurement path optimization method incorporating slope constraints. [Methods] The method establishes a mathematical model that considers the gradient of the bank slope，the geometric parameters of the vessel，and the detection range of the transducer to calculate the optimal safe distance between the hull and the shoreline.By integrating the river centerline and water level line，the measurement path is optimized to balance operational safety and data completeness. [Findings] The river cross-section measurement experiments results indicate that with fixed vessel dimensions and transducer detection limits，the slope of the bank is the primary factor influencing the safe distance.Compared to traditional measurement paths，the optimized path enables dynamic adjustment of the safety distance based on slope variations.Compared with the original measurement results，the data volume collected along the optimized path has increased by 0.039% to 0.797%，enabling more comprehensive data acquisition and effectively addressing the issue of data omission associated with traditional single beam sounding in complex terrains. [Conclusions] This method effectively balances hull safety and data completeness，making it suitable for nearshore environments with non-vertical slopes.It offers advantages such as low hardware cost and high operational efficiency，providing a scalable theoretical framework for nearshore water depth inversion using single beam unmanned vessels.Future research may integrate unmanned vessels with 3D modeling modules for real-time slope terrain analysis and employ artificial intelligence for nearshore underwater data prediction．

Key words: single beam, unmanned vessel, water depth measurement, nearshore measurement, slope, path planning