Electroreduction of CO2 has become the most attractive approach to generate value‐added chemicals and fuels. Products of single atomic catalysts (SAC) in CO2 reduction reaction reactions (CO2RR) are mostly limited to CO since the contributions of spatial and thermodynamic factors are not distinguished. To break through the challenges, comprehensive explorations in graphdiyne(GDY)‐based SAC are made, to reveal detailed influences of active sites, elements, and adsorptions on the selectivity and reaction energy of the C1 pathway. Unique d electrons dominated adsorption behaviors are identified, where the d6 boundary is able to help screen out promising candidates for achieving complicated C2+ products. Based on spatial and thermodynamic factors, metal sites are still the most promising active sites. The transition metal based GDY‐SACs show element‐dependent electroactivity towards different products in CO2RR. Meanwhile, the GDY‐Pr and GDY‐Pm SACs are promising candidates for the CO2RR and even C2 products in the future. This work supplies in‐depth insights into the CO2RR to facilitate the design of efficient atomic catalysts in future work.