A new resonance Rayleigh scattering method was developed for the determination of melamine in milk using gold nanoparticles as spectral probe. Under certain conditions, melamine can form bigger aggregate with gold nanoparticles, which resulted in great enhancement of resonance Rayleigh scattering. Based on optimizing various parameters, the linear dynamic range, the Regression equation, the linear correlation and the detection limit were 3.3×10^－8～4.7×10^－7 mol/L, ΔI_RRS＝106.98C－28.279, R²＝0.9971 and 2.7×10^－8 mol/L, respectively. In this method, the gold nanoparticles do not need to be decorated. Only an amount of single-strand oligonucleotide (T₁₀) need to be added to the system. The experiments showed that this developed method is practical, simple, sensitive and selective.