Abstract: Purpose Unmanned surface vehicles (USVs), as key platforms in marine intelligent robotics, often adopt waypoint-based navigation for practicality, but large initial position deviations and discontinuous reference trajectories make conventional guidance methods prone to slow or unstable tracking and overshoot at waypoints. MethodA waypoint-smoothing mechanism is proposed using circular-arc transitions to ensure trajectory continuity and differentiability. An optimal virtual guiding vessel mechanism is formulated via quadratic programming to minimize position error while considering USV maneuverability, enabling smooth, rapid trajectory entry. A line-of-sight guidance law based on fixed-time prescribed performance control is then designed to accommodate the dynamics of the virtual vessel. Results Matlab simulations and sea experiments on a 4.9 m USV demonstrate fast and smooth trajectory tracking under various initial deviations, effectively suppressing overshoot at waypoints and ensuring constrained error convergence. Conclusion The proposed method guarantees fixed-time stability while satisfying maneuverability constraints and strictly bounding tracking errors, highlighting its potential for practical engineering applications.