Background & Aims of the Study: Azo Dyes are the most hazardous materials in different industries. Dyes and pigments used in industries for applications such as textiles, leathers, papers, foodstuffs, additives, etc. Application amounts of azo dyes in industries which can cause severe health problems in human and environmental pollutant problems. So, color wastewaters decomposition plan are necessary. The purpose of this study is the application statistical experimental design in photocatalytic decomposition of azo dye Acid Red 14 (AR14) from aqueous solutions using multi walled carbon nanotubes (MWCNTs) particles which was used UV/H2O2 process in photoreactor. Materials & Methods: MWCNTs particles as a catalyst used for the degradation of dye in aqueous solution. MWCNTs particles have been characterized by scanning electron microscopy (SEM), Transmission Electron Microscopy (TEM) and Fourier transform infrared (FT-IR). Design of experimental (DOE) based design matrix was exerted for measure the effect of these three factors such as: A) pH, B) catalyst amount and C) H2O2 concentration at two levels. The full factorial experimental design was utilized in this process. The significant effects of each factor and interactions determined using analysis of variance (ANOVA) method. The decomposition kinetic of dye was studied. Results: The maximum photocatalytic degradation efficiency of dye obtained in this study was found 90. 65%, corresponding to the optimal conditions of 3, 30 mg L-1 and 20 ppm respectively, for the pH, catalyst amount and H2O2 concentration. The most effective factor in the photocatalytic degradation efficiency was H2O2 concentration. The interaction between pH×H2O2 concentrations was the most effective interaction. A pseudo first order reaction with a rate constant (k=0. 0696 min− 1) was observed for the photocatalytic degradation of dye. Conclusions: The results showed that photodegradation process can be suitable alternative to degradation dyes in aqueous solutions.