As a promising technology for water purification, solar desalination requires high maintenance to remove accumulated salt deposits; otherwise, the evaporation efficiency and functioning of the system will deteriorate. Here, we develop a facile auto-cleaning photo-thermal membrane for water desalination and illustrate its corresponding principles. The membrane is constructed by polypyrrole shells anchored onto cellulose fiber (PCF) paper and displays super-hydrophilicity, hydrostability and robust light absorption. In particular, the super-hydrophilic product with high porosity (80%) can stably bind abundant water and provide an efficient passageway to spontaneously transfer the scaled salt back to the bulk seawater in the dark. In addition, the PCF with abundant channels for water transport exhibited an extremely high light-to-vapor efficiency of 90% without sunlight concentration. With a high and constant evaporation flux of 1.41 kg m(-2) h(-1) (seawater salinity) over days of evaporation cycles without manual cleaning, the as-prepared photothermal membrane is expected to be competent for stable long-term solar desalination. In addition, it is easy to scale-up the production of this evaporator, with a low cost of approximately $ 1.33/m(2). The present development, which is easy to scale-up, has a low cost, is highly efficient and features auto cleaning, is an important practical desalination technology.