Decolourisation of Anionic cum acidic azo dye Amaranth was carried out by an Advanced Oxidation Process Solar/H2O2. Dye samples of concentration 100 mg/L was taken in 250 ml conical flasks that were treated with 30% H2O2 and exposed to sun light in the intensity range of 60,000-90,000 lux. The impact of various parameters in decolourisation of dye like initial H2O2 concentration, initial dye concentration, initial pH, solar light intensity, additives and temperature was studied in view of kinetics. All the reactions carried out by the impact of system parameters follow pseudo-first order kinetics. Conditions were optimized, and the optimum pH was found to be 12 with an optimum H2O2 concentration of 650 mM to achieve 100% decolourization in 30 minutes. Impact of additives can be studied by adding chloride and dihydrogen phosphate ion of 1 M concentration. Then, mineralization is studied by COD removal. UV-visible spectrometric analysis is done to study degradation level.