Merapi is an active volcano on the border of DIY - Central Java. The eruption that occurred at Mount Merapi has caused a change in the condition of the soil and vegetation in the surrounding it. This study aims to identify the distribution of vegetation after the 2010 eruption in the geomorphic unit of the middle slope of the southern flank of Mount Merapi. This study used a survey method that is analyzed descriptively and spatially. Analysis conducted to determine vegetation diversity through determination of the value of density, frequency, dominance, important value index, and diversity index. The results of the study showed that in the geomorphic unit on the middle slope of the southern flank of Mount Merapi located in the Disaster-Prone Areas II and III was composed of 33 species with 209 individuals. The highest species diversity is in the Batur study area. The species that dominates this region is Sengon (Albizia chinensis) that function to accelerate the succession because Sengon is the species that able to survive in critical land conditions and is also able to bind with Nitrogen-binding bacteria. The more nitrogen contained, the succession process will be faster.