Polyaniline (PANI)-doped fin oxide-diatomite hybrid photocatalysts were synthesized by the adding of fin source and diatomite silica support to prepared PANI solution via chemical oxidative polymerization of aniline monomer. The obtained catalysts were characterized with X-Ray diffraction (XRD), nitrogen adsorption-desorption isotherm, scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) and UV visible diffuse reflectance spectrums (UV-vis DRS) analyses techniques and tested in the photodegradation of Remazol Yellow (RY) dye under UV light. The characterization results showed the evidence of interaction between PANI, diatomite and fin oxide. The TEM images showed that fin settled as nanoneedles and nanograins on the solid surface. The adding of calcined diatomite-fin solid to the PANI solution resulted in high surface area, pore volume and large pore diameter values and also the indirect band gap energy determined by Tauc's plot was decreased. The degradation of RY was reached 96% within 1 h at 1 g/L catalyst dose. The degradation kinetics of RY in all cases was found to be pseudo-first-order kinetics model. It has been found that the band gap energy has a significant effect on the photocatalytic activity.