A novel colorimetric method for the detection of tyrosinase (TYR) and its inhibitor by taking utilization of Ag⁺−3,3′,5,5′-tetramethylbenzidine (TMB) detection system has been proposed. Ag⁺ could oxidize TMB to oxidized TMB (oxTMB) and induce a blue color solution corresponding to an absorption peak centered at 652 nm. The addition of dopamine (DA) could cause the reduction of oxTMB which resulted in the fading of the blue color and a decrease of the absorbance at 652 nm. However, in the presence of TYR, DA could be oxidized to dopaquinone, which inhibited the reduction of oxTMB by DA, resulting in a blue color recovery and an increase of the absorbance at 652 nm. Based on this finding, we propose a method to quantitatively detect TYR activity with the help of UV–vis spectroscopy. The developed assay is highly sensitive with a low detection limit of 0.010 U/mL. More importantly, this method is fairly simple and inexpensive without the use of complicated nanomaterials. In addition, it constructs a useful platform for TYR inhibitor screening.