In recent years, Molten carbonate electrolysis cell(MCEC) has attracted increasing attention since it can generate the hydrogen via the simultaneous electrolysis of H₂O and CO₂ at cathode at a relatively low temperature (620℃). When MCEC is combined with steam methane reforming (SMR), the high purity hydrogen (>98%) can be produced with high efficiency compared to SOEC (solid oxide electrolysis cell), SMR and PEMEC (polymer electrolyte membrane electrolysis cell). The conventional SMR catalyst for this hybrid system (MCEC+SMR) is the Ni metal. However, when the electrolyte such as Li₂CO₃ and Na₂CO₃ in the MCEC evaporates, it blocks the active site of the Ni catalyst and in turn reduces the activity of the catalyst. Thus, it is imperative to develop the electrolyte tolerant SMR catalyst for the stable operation of MCEC/SMR hybrid system. In this study, by density functional theory (DFT), we designed the Ni-based alloy catalysts to prevent the catalyst poisoning by Na₂CO₃ electrolyte. First, we examined the effect of electrolyte on the SMR activity on model Ni(2 1 1) surface and developed the multi-scale model for the novel catalyst design by deriving the descriptors for representing the SMR activity, alloy stability and electrolyte-poisoning. Second, using the multi-scale model, we screened the Ni-based novel catalysts through composition and ligand engineering. We found that Ni₃Co(2 1 1), Ni₃Zn(2 1 1), Ni₃Rh(2 1 1), Ni₃Pd(2 1 1), Ni₃Ir(2 1 1), Ni₃Pt(2 1 1), NiZn(2 1 1), NiRh(2 1 1) can be promising candidates for enhancing the electrolyte tolerance with high SMR activity. Especially, NiZn(2 1 1) has lowest SMR activity with electrolyte poisoning. This is due to the weaker adsorption of carbon (carbon coking), resulting in improved performance of SMR reaction. In addition, by using electronic structure calculation, we also found that Ni and Zn rarely interact electronically due to their large energy level difference, so the energy of d-orbital is low. This study provides the insight on the impact of alloy effects in preventing the catalyst poisoning by molten alkali metal carbonates.