Abstract: A method for healing a damaged separation membrane for water treatment uses silica microparticles surface-functionalized with polyethyleneimine. The method can be applied to actual water treatment processes because the particle size and chemical stability of the silica microparticles surface-functionalized with polyethyleneimine are maintained under various operation conditions are used. A separation membrane for water treatment healed exhibits superior healing performance, with water permeability and rejection rate being healed to 90% or higher as compared to the pristine separation membrane, and maintains physical and chemical stability for a long time. Moreover, the method is advantageous in that flux does not declines after the healing because the silica microparticles surface-functionalized with polyethyleneimine are selectively deposited on the damaged part. In addition, it is advantageous in terms of economy in that silica microparticles commercially available at low cost are used.