The paper presents a simple fabrication method of porous silica xerogel films. By adding a surface active agent Triton X-100™ to the starting solution, we can considerably reduce the surface tension, which, in turn, allows to fabricate silica films of high porosity. The paper presents the influence of surfactant content and the influence of heating temperature on the refractive index and thickness of the fabricated films. We fabricated silica films of the minimum refractive index below 1.3 and corresponding porosity ∼50%. Due to low refractive index, the elaborated porous silica xerogel films can be applied to reduce the light reflection coefficient in optical systems. In this work the spectral characteristics of the refractive index, extinction coefficients, the reflection and transmission coefficients and also depolarization factor are presented. The paper also provides results of surface morphology of produced layers, obtained using an atomic force microscope.