The semi-hydrogenation(deuteration) of alkynes plays an essential role in high-value chemical production, and the reaction mechanism between H and D remains elusive. In this work, advanced microkinetic modeling is combined with the energetics from the first principles calculation to investigate the activity and selectivity of acetylene hydrogenation (acetylene-d2 deuteration) on Ag nanoparticles. By constructing a polyhedral model, it can be found that the olefin production on Ag nanoparticles converged when the size was at the diameter of 6 nm. Furthermore, it is found that the effective production rates are contributed by Ag(100) and Ag55 (corner site). The temperature considerably affects the free reaction energy (ΔG) between hydrogenation and deuteration. Consistent with the experiment, our kinetic simulations indicate that hydrogenation gives rise to a reaction rate approximately 3 times larger than the TOF of deuteration.