In this article modeling of dissociative adsorption of hydrogen on Pd (1 1 1) surface by ultra-accelerated quantum chemical molecular dynamics (UA-QCMD) was reported for the better understanding of the role of hydrogen vacancy for the dissociative adsorption of hydrogen. Here we have demonstrated and examined the isolated steps of hydrogen dissociative adsorption on Pd (1 1 1) surface. The direct observations of dissociative adsorption of hydrogen on Pd (1 1 1) surface (different vacancy models) were successfully simulated. From the analysis of the change of electronic structures and the dynamics of dissociative adsorption process, we can conclude that divacancy sites are inactive for dissociative adsorption of hydrogen on Pd (1 1 1) surface. Our findings suggest that H-2 dissociation on Pd (1 1 1) requires an ensemble of at least three hydrogen vacancies. Our results support the original interpretation of STM work of Mitsui et al. that three or more hydrogen vacancy is required for dissociative adsorption of hydrogen. (C) 2010 Elsevier B. V. All rights reserved.