A 3D-printed bionic hydrogel evaporator (3DP-BHE) is developed for efficient and stable solar desalination. Inspired by tree transpiration and hierarchical porous structures, the 3DP-BHE uses commercialized activated carbon (AC) embedded in a biomass starch skeleton to achieve cost-effective and scalable production. The bionic tree leaf layer provides high light absorption (94.01%) and vapor diffusion, while the bionic tree trunk layer with a 3D-printed bimodal porous structure facilitates water transport, thermal isolation, and salt ion convection. The 3DP-BHE achieves a stable evaporation rate of 2.13 kg m⁻² h⁻¹ under one sun (1 kW m⁻²) with 90.5% energy efficiency. During 7-day desalination of 10 wt.% brine, it maintains a steady evaporation rate of 1.98 kg m⁻² h⁻¹ with a record-high cost-effectiveness of 195.3 g h⁻¹ $⁻¹. The 3DP-BHE offers a low total material cost of 10.14 m⁻² and demonstrates excellent salt resistance through synergistic diffusion and convection. It effectively prevents salt crystallization on the evaporator surface by creating a concentration gradient and reducing salt transport resistance. The 3DP-BHE also shows high thermal isolation, with a thermal conductivity of 0.64 W m⁻¹ K⁻¹, and efficient solar-to-vapor conversion. The evaporator's performance is validated through various characterizations, including rheological properties, SEM imaging, and ion concentration analysis. The 3DP-BHE outperforms conventional hydrogel evaporators in terms of evaporation rate, energy efficiency, and cost-effectiveness. It is suitable for practical applications in multiple scales, from individual households to off-grid communities. Future research aims to enhance the evaporator's durability and resistance to microbial contamination in ocean environments.A 3D-printed bionic hydrogel evaporator (3DP-BHE) is developed for efficient and stable solar desalination. Inspired by tree transpiration and hierarchical porous structures, the 3DP-BHE uses commercialized activated carbon (AC) embedded in a biomass starch skeleton to achieve cost-effective and scalable production. The bionic tree leaf layer provides high light absorption (94.01%) and vapor diffusion, while the bionic tree trunk layer with a 3D-printed bimodal porous structure facilitates water transport, thermal isolation, and salt ion convection. The 3DP-BHE achieves a stable evaporation rate of 2.13 kg m⁻² h⁻¹ under one sun (1 kW m⁻²) with 90.5% energy efficiency. During 7-day desalination of 10 wt.% brine, it maintains a steady evaporation rate of 1.98 kg m⁻² h⁻¹ with a record-high cost-effectiveness of 195.3 g h⁻¹ $⁻¹. The 3DP-BHE offers a low total material cost of 10.14 m⁻² and demonstrates excellent salt resistance through synergistic diffusion and convection. It effectively prevents salt crystallization on the evaporator surface by creating a concentration gradient and reducing salt transport resistance. The 3DP-BHE also shows high thermal isolation, with a thermal conductivity of 0.64 W m⁻¹ K⁻¹, and efficient solar-to-vapor conversion. The evaporator's performance is validated through various characterizations, including rheological properties, SEM imaging, and ion concentration analysis. The 3DP-BHE outperforms conventional hydrogel evaporators in terms of evaporation rate, energy efficiency, and cost-effectiveness. It is suitable for practical applications in multiple scales, from individual households to off-grid communities. Future research aims to enhance the evaporator's durability and resistance to microbial contamination in ocean environments.