Green synthesis of Ag NPs were successfully achieved using root bark extract of Catunaregum spinosa. Ag nanomaterials are in size of 38 nm with spherically agglomerated particles. Green synthesized Ag NPs were acted as photocatalyst for degradation of food azo dye Amaranth. Pseudo first order kinetic reaction were successfully processed for photocatalytic activity with 94.07% of degradation.