A multicolor visual method for the detection of hydrogen peroxide (H2O2) was reported based on the iodide-mediated surface etching of gold nanostar (AuNS). First, AuNS was prepared by a seed-mediated method in a HEPES buffer. AuNS shows two different LSPR absorbance bands at 736 nm and 550 nm, respectively. Multicolor was generated by iodide-mediated surface etching of AuNS in the presence of H2O2. Under the optimized conditions, the absorption peak Δλ had a good linear relationship with the concentration of H2O2with a linear range from 0.67~66.67 μmol L−1, and the detection limit is 0.44 μmol L−1. It can be used to detect residual H2O2in tap water samples. This method offered a promising visual method for point-of-care testing of H2O2-related biomarkers.