H-index is used originally to evaluate and characterize the scientific output of a researcher. The major strength of h-index is that it takes into account both the quantity and quality of one researcher's output, as represented by his or her number of publications, and citations they receive, respectively. A ranking of the worlds' top universities and research institutions based on their h-index scores was produced. Then the geographic distributions by continents and by countries of the highly ranked universities were discussed. Regarding the applicability of the h-index at the institutional level, it is found that a high correlation between the ranking of h-index and that produced by Shanghai's Jiao Tong University (JTU). The results suggest that the validity of the h-index in the assessment of research performance at the institutional level.