Abstract: Based on Ag-Au spherical nanocages with peroxidase-like activity, a colorimetric method for the determination of GSH and GST was developed. Ag-Au nanocages catalyzed the reaction of TMB with H₂O₂, a clear UV-vis absorption peak was observed at 652 nm, and the solution color changed from colorless (TMB) to blue (oxTMB). When GSH existed, oxTMB was reduced to TMB by GSH, the absorbance at 652 nm decreased and the color changed from blue to light. When GST existed, GST specifically bound with GSH, which effectively inhibited the reduction of oxTMB by GSH, resulting in an increase of absorbance at 652 nm, and the solution color changed from colorless to blue. Under the optimal conditions, the linear range of GSH and GST detection was 0.5−1 μmmol/L (R² = 0.986) and 1−50 μg/mL (R² = 0.999), respectively. This method was of good selectivity, and was applied to the determination of GSH and GST in serum samples with satisfactory results.