The invention relates to the field of materials technology and provides a modified nano-silica and a method for preparing the same, a pigment dispersion and a photosensitive resin composition, so as to solve the problem that conventional nano-silica cannot crosslink with other polymeric materials, and pigment dispersions are apt to aggregate and have a poor film-forming property. The modified nano-silica according to the invention has unsaturated double bonds on the surface thereof and can crosslink with other polymeric materials, such that the pigment dispersion comprising the modified nano-silica can effectively prevent agglomeration and has a good film-forming property, and the photosensitive resin composition comprising the pigment dispersion can reduce the thermal expansion of a film made thereby, as well as the occurrence of shrinkage and collapse phenomena in the surface of the film, and enhance the heat-resistance, chemical-resistance, mechanical properties and abrasion-resistance of the film.