Abstract: To clarify the energy-loss mechanisms of a low-head axial-flow Kaplan turbine under different operating conditions and support coordinated optimization and intelligent control, this study investigates a low-head axial-flow Kaplan turbine. Steady-state entropy-generation distributions under various combinations of runner-blade angles and guide-vane openings were systematically analyzed using CFD simulations based on the RNG k-ε turbulence model, and pressure-pulsation tests were conducted to validate the numerical results. The results show that the runner is the dominant region of entropy generation, accounting for up to 81% of the total entropy generation. The suction side of the blades is the primary zone of energy dissipation. The coordinated variation of guide-vane opening and runner-blade angle markedly affects both the spatial entropy-generation distribution and the overall entropy-generation level. At small guide-vane openings, the total entropy generation rises significantly, and the region of irreversible losses shifts from the draft tube to the runner. Pressure-pulsation test results show that flow pulsations become more intense at larger runner-blade angles and are closely associated with regions of high entropy generation. The spatial migration patterns of energy losses and the component-coupling mechanism are revealed in this study. These findings provide a theoretical basis and technical support for the coordinated optimization of low-head axial-flow Kaplan turbine design and the formulation of operating strategies.