The traditional surfactant sodium dodecyl sulfate(SDS) and ionic liquid 1-ethyl-3-methylimidazolium tetrafluoroborate([Emim][BF4]) have been combined to create a novel efficient medium for chromogenic catalysis of 3,30,5,50-tetramethylbenzidine with horseradish peroxidase in presence of H_2O_2. The results have shown the [Emim][BF_4] in the mediums can promote the rate of formation of the blue chromogen,the SDS is responsible for the stabilization of the blue chromogen due to the electrostatic attraction between positively charged blue chromogen and the negatively charged surfactant. The SDS/[Emim][BF_4]combination not only enhance catalytic activity of HRP remarkably but also stabilize the blue chromogen formed in the HRP oxidation of the substrate TMB compared to the conventional medium. Based on the superior combination of SDS and [Emim][BF_4], the colorimetric assay for detecting HRP activity and H_2O_2 concentration was established. This work demonstrates a novel efficient medium for chromogenic catalysis with potential applications in biosensors and clinical diagnosis. The traditional surfactant sodium dodecyl sulfate (SDS) and ionic liquid 1-ethyl-3-methylimidazolium tetrafluoroborate ([Emim] [BF4]) have been combined to create a novel efficient medium for chromogenic catalysis of 3,30,5,50-tetramethylbenzidine with horseradish peroxidase in presence of H 2 O 2. The results have shown the [Emim] [BF_4] in the mediums can promote the rate of formation of the blue chromogen, the SDS is responsible for the stabilization of the blue chromogen due to the electrostatic attraction between positively charged blue chromogen and the negatively charged surfactant. The SDS / [Emim] [BF_4] combination not only enhance catalytic activity of HRP remarkably but also stabilize the blue chromogen formed in the HRP oxidation of the substrate TMB compared to the conventional medium. on the superior combination of SDS and [Emim] [BF_4], the colorimetric assay for detecting HRP activity and H_2O_2 concentration was established. This work demonstrates a novel efficient medium for chromogenic catalysis with potential applications in biosensors and clinical diagnosis.