The aim of this work focused on the preparation of Mn2+ doped on TiO2 by impregnation method for the photocatalytic degradation of Reactive Red-3 dye aqueous solution. Characterizations of the photocatalyst were carried out by using XRD, BET, SEM and UV-DRs. The extended photocatalysis were studied as functions of %wt Mn2+ (0%, 0.05%, 0.1%), pollutant concentration, solution pH and catalyst loading using Response Surface Method (RSM) based on Box-Behnken design. Based on results found that the anatase phase was not affected by Mn2+ added on the surface of TiO2 whereas the rutile phase increased with increasing Mn2+ contents. The band gap energy of Mn2+ doped on TiO2 did not show in red shift but it exhibited higher absorbance than neat TiO2 in visible region. The surface area was insignificantly changed for Mn2+ doped on TiO2. The degradation results were investigated that pollutant concentration, pH of solution and loading of Mn2+ on TiO2 were significant parameters effecting on photocatalytic degradation of Reactive Red-3 dye. The existence of Mn2+ on TiO2 decreased the activity of rectaion. The optimum condition was 0%wt of Mn2+, 10 ppm of Reactive Red-3, pH 4 and 4.0 g/L of catalyst loading.