The invention discloses a Ag+ colorimetric detection method based on an analyte catalyzed nanoparticle synthetic reaction. According to the method, the reaction that low-concentration o-phenylenediamine can effectively mediate agglutination of gold nanoparticles with surfaces provided with negative charge, and consequently the reaction solution turns blue from red is utilized. A small amount of Ag+ can efficiently and specifically oxidize o-phenylenediamine into 2,3-diaminophenazine, meanwhile, Ag+ is reduced to generate nano silver particles, the nano silver particles further catalyze o-phenylenediamine to generate 2,3-diaminophenazine, and therefore the metachromatism is inhibited. The agglutination degree of the gold nanoparticles is inversely proportional to the Ag+ concentration in a sample. Therefore, the qualitative or semi-quantitative detection of Ag2+ can be achieved by observing the color change of the reaction solution with the naked eyes. Quantitative detection of Ag2+ can be achieved through an ultraviolet and visible spectrophotometer. The method can be directly applied and popularized to simple, economical, fast, sensitive and specific analysis and detection of Ag2+ analyte in various samples in multiple fields such as medical diagnosis, environmental monitoring and food safety.