This paper aims to study the indices of Inter-provincial migrations by use of migration's spatial structure model and mobility transition theory of Zelinsky, in Iran during 1976-2006. The study focuses on five conceptual aspects of inter-provincial migrations which include intensity, effectiveness, concentration, connectivity and distance of inter-provincial migrations. The results taken from Migration Effectiveness Index indicate that the effect of inter-provincial migrations on population redistribution and mig-reproduction rate has reduced during 1976-2006. In addition, the inter-provincial migration connectivity over the same period has increased. Levels and trends of migration centrality indices indicate that centrality in Iran's migration system has reduced in recent decade. Additionally, a stable pattern is observed for migration distances.  
Changes of in and inter-regional inequality of per capita incomes, the increase of communications facilities and changes in regional population growth rates have been basic determinants of Iran's migration spatial structure.