Due to its potential applications in ultra-sensitive sensing, metamaterials, optical switches, and nonlinear optical devices, Fano resonance in plasmonic metal nanostructures has attracted extensive attention. However, experimental studies on the Fano resonance of metal nanodimers at a single particle scale are still scarce. In this paper, Fano resonance phenomenon in Au-Au nanorod dimers is investigated experimentally using single-particle spectroscopy. The longand short Au nanorods with resonance peaks at 1 060 nm and 700 nm in water are synthesized by the seed growth method, their average lengths are 110 nm and 55 nm, corresponding to average diameters of 17 nm and 20 nm respectively, and the Au-Au nanorod dimers are constructed by electrostatic adsorption self-assembly of L-cysteine molecules. When mixed short and long gold nanorods solution is added with 0.9 mmol/L L-cysteine, the cysteine preferentially binds to the ends of the gold nanorods through the sulfydryl group, and due to the mutual attraction of positive and negative charges, the amphoteric ionic groups assist the two nanorods to interconnect through end-to-end electrostatic adsorption, thus forming a dimer. Scattering spectra of a singleAu-Au nanorod dimer before and after coupling are measured by dark-field microscopy and theoretically simulated by the finite difference time domain (FDTD) method. The near-field electromagnetic distribution images of nanodimers are also analyzed. Dark-field scattering spectrum shows that the destructive interference between the bright dipole mode of a short Au nanorod and the dark quadrupole mode of a long Au nanorod produces an obvious Fano resonance dip at 660 nm, and the theoretical simulated scattering spectrum is in good agreement with the experimental one. The electromagnetic distribution images show that the electric field enhancement of the bright dipole mode of a short Au nanorod is descend at the Fano dip (656 nm), while the dark quadrupole mode of a long Au nanorod is enhanced, which is also the result of the destructive interference of the two Au nanorods. These self-assembled Au-Au nanorod dimers have a broad application prospect in plasmonic sensing and detection.