In the present study, the Box-Behnken design in the response surface methodology (RSM) was availed to investigate the modelization and optimization of Methyl Orange (MO) mineralization parameters. The process was carried out in the presence of lanthanum (La) doped mesoporous titanium dioxide (TiO2) by a simple impregnation method using various La doping amounts (0.5, 1.5 and 3 wt%). The physico-chemical characteristics of each catalysts are studied under several approaches. The effects of the wavelength of irradiation light, catalysts weight and MO concentration on the yield of MO mineralization were investigated. Based on ANOVA analysis, the results show that the response of MO mineralization (R) in photocatalytic process was significantly affected by a positive individual effect of wavelength and catalyst weight. However, the individual effect of MO concentration has an antagonist impact through the whole process. The optimum conditions were achieved for the light irradiation wavelength of 310 nm, catalyst weight of 80 mg, and MO concentration of 20 ppm, which allowed reaching 99.89 % of mineralization. Overall, the adjusted coefficient of determination (R2) value of 0.9956 indicated that the used model was quite suitable and the selected RSM was successful in optimizing the mineralization conditions of MO.