Based on the unique physical properties of noble metal nanoparticles, a fluorescence sensor with signal amplification function was designed for detecting the concentration of dopamine. Based on the effect of metal fluorescence enhancement, the fluorescence signal was amplified by adding a spacer layer between the gold nanoparticles and fluorophore. First, the aptamer chemically modified with an SH bond was mixed with a gold nanoparticle solution to form a stable Au-S bond structure. Then, the DNA labeled with fluorescent groups were bound due to the complementary base pairing. The distance between the fluorophore and the surface of the gold nanoparticle was adjusted by changing the amount of base A. At the same time, the concentration ratio between the aptamer and gold nanoparticles and the pH of the reaction environment were optimized to obtain the best amplification efficiency. Finally, different concentrations of dopamine were tested. The experimental results indicate that at a certain concentration ratio between the gold nanoparticle solution and aptamer, the maximum fluorescence enhancement is 2.35 times at the isolation layer thickness is 27 base A. Dopamine concentration detection has a linear range of 20-100 nmol/L. The detection limit is 20 nmol/L. It can effectively regulate the isolation layer thickness at the nanometer level, providing a stable signal amplification strategy.