Employing the oxidative coupling of phenylacetylene with benzaldehyde as a model reaction, a density functional theory (DFT) study combined with extended X-ray absorption fine structure (EXAFS) experiment was carried out to reveal the difference between dinuclear and mononuclear zinc mediated nucleophilic addition. Newly reported DFT method M11-L computed results suggest that the mononuclear zinc mediated pathway, in which nucleophilic addition occurs via a four-membered ring transition state, is unfavorable both thermodynamically and kinetically. The dinuclear zinc mechanism, which properly explains the experimental observations, involves a six-membered ring transition state for nucleophilic addition. Subsequent in situ EXAFS experiment confirmed the existence of dinuclear zinc active species. Moreover, frontier molecular orbital (FMO) analysis and distortion-interaction energy analysis along the whole reaction pathways have provided interpretations for the advantage of dinuclear zinc mediated nucleophilic addition. Consequently, we believe this dinuclear zinc pathway will open up a general consideration of dinuclear zinc mechanism for nucleophilic additions.