Abstract: Abstract: Currently, the global demand for freshwater resources is continuously increasing. As the most abundant water source, seawater desalination has become a critical approach to alleviating freshwater shortages. In this study, a self-floating biomass-based solar evaporator (SE) was constructed using coniferous pulp fibers (CF) as the framework, crosslinked with chitosan (CS) and sodium alginate (SA), and incorporated with polystyrene (PS) particles to enhance self-floating capability and thermal localization performance, followed by freeze-drying. With an optimized truncated pyramid structure, the evaporator exhibited excellent evaporation efficiency and stability in interfacial solar evaporation. Under 1 sun irradiation, the SE achieved an evaporation rate of 2.12  kg·m⁻²·h⁻¹ in a 3.5wt% NaCl solution, with an evaporation efficiency of 118.5%. The removal rates of Na⁺, K⁺, Mg²⁺, and Ca²⁺ all exceeded 99.9%. This study demonstrates that the biomass-based evaporator possesses promising seawater desalination performance and good salt crystallization resistance, providing a feasible approach for sustainable freshwater supply.