Improving the desalination performance of the solar evaporator is the core of promoting the application of sustainable solar desalination technology. In this study, a flower-inspired bionic evaporator was successfully prepared, the bundled of black hollow sodium alginate hydrogel tubes were fixed vertically to form a flower structure with branched hydrogel tubes at the top. The prepared black flower hydrogel evaporator showed the excellent evaporation rate of 3.2 kg m−2 h−1, and the salt crystallization phenomenon during solar desalination was effectively suppressed. Three-dimensional flower configuration of the hydrogel tube with the appropriate length could increase the effective evaporation area and accelerate the evaporation process. Moreover, the hollow hydrogel network structure exhibited the stable water supply capacity to promote salt ions exchange at the evaporation interface, thereby inhibiting salt crystallization phenomenon. This study proved that constructing a 3D-shaped evaporator is an effective way to subversively improve the solar desalination performance for application.