Designing and fabricating atomically uniform active sites toward favorable adsorption configuration of essential species to match specific reaction pathways is of great importance in catalytic semihydrogenations, yet it remains challenging. In this research, we present a straightforward method for synthesizing a CoSb intermetallic catalyst through the structural conversion of layered double hydroxide precursors, optimizing Co sites for configuration matching in propyne semihydrogenation. Characterizations using X-ray diffraction, high resolution transmission electron microscopy, and X-ray absorption spectroscopy demonstrate the formation of P6₃/mmc CoSb intermetallic phase. The CoSb intermetallic catalyst, with its well-organized atomic surface and optimized electronic structure, achieves 97.0% propylene selectivity with nearly complete propyne conversion. Temperature-programmed surface reaction and desorption measurements, along with theoretical calculations, unravel that this exceptional selectivity arises from the kinetically preferred desorption of propylene over its further hydrogenation to undesired propane byproduct on the finely regulated Co sites of the CoSb intermetallic catalyst.