Abstract: Interface solar steam generation technology provides an efficient and sustainable strategy for extracting fresh water from seawater and wastewater, which can effectively solve the current water crisis. In present work, diatomite based porous ceramics were prepared by grouting molding process by using natural diatomite as the main raw material and CaCO₃ as the pore forming agent. Then, carbon nanotube/diatomite based porous ceramic composites were prepared successfully by surface modification of the diatomite based porous ceramics coating with the multi walled carbon nanotubes and sodium alginate mixed gel. Characterizations confirm that the diatomite based porous ceramics have a three-dimensional connected porous structure, and the pore size is mainly 10-30 µm. When the mass fraction of CaCO₃ is 50wt%, the porosity can reach 73.2%. Owing to the multiple scattering effect and hydrophilicity of the porous structure and the excellent photothermal conversion ability of carbon nanotubes, the evaporator show excellent properties. Under one solar intensity, the evaporation rate and energy conversion efficiency of the evaporator are up to 2.07 kg·m⁻²·h⁻¹ and 95.6%, respectively and maintains good cycle stability. Additionally, the ion rejection rate of seawater and wastewater for the evaporator can achieve nearly 100%. It shows broad application potential in the field of seawater desalination.