Understanding the mechanism of the nitrogen reduction reaction (NRR) is essential for designing highly efficient catalysts. In this study, we investigated the effects of the metal–support interaction (MSI) on NRR using density functional theory. The simulations revealed that the MSI is weak in the Au13/BiOCl system, with charge accumulation and depletion primarily occurring within the Au13 cluster. By replacement of one Au atom with either a Ag or Pt atom, the MSI becomes stronger compared to that in the Au13/BiOCl system. The is because doping breaks the symmetry of the Au13 cluster, leading to charge accumulation and depletion at the interface. Specifically, this enhanced MSI reduces the energy barriers of the rate-determining step from 1.07 eV in the Au13/BiOCl system to 0.91 eV in Au12Ag/BiOCl and 0.87 eV in Au12Pt/BiOCl, respectively. Our study uncovers the critical role of MSI in the activity of NRR, providing theoretical insights for the development of highly efficient NRR catalysts.