Abstract: A non-aggregation colorimetric method for the rapid determination of dopamine (DA) has been developed based on the fact that DA can reduce Ag⁺ to Ag on the surface of gold nanorods (AuNRs) to form Au core-Ag shell nanorods (Au@AgNRs) in a AuNRs-Ag⁺-DA system, which leds to the change of dielectric function: the aspect ratio of AuNRs decreases, the longitudinal plasmon absorption band (LPAB) of AuNRs blue shifts (Δλ), and the color of the solution changes obviously. The method has been successfully applied to the detection of DA in serum, and the results were in a good agreement with those determined by the fluorescence method. The mechanism for the detection of DA has also been discussed.