Karst topography has high susceptibility to degradation due to human disturbance. During the last decade, much effort has been made to recover the vegetation in the region of southwest China characterized by karst topography. However, the recovery varies regionally. This study was aimed to assess the impacts of bedrocks on vegetation dynamics. Soil in the karst region of southwest China was mainly derived from limestone and dolomite bedrocks. A natural reserve was selected as the study area to examine the geological control on vegetation change. We classified the Landsat TM5 data recorded in 1990 and 2011 using a supervised classification method for stages of succession of natural vegetation and image characteristics of karst region. We then analyzed spatial patterns to identify the differences in vegetation change rate and direction for two different rock types (limestone and dolomite). In both cases, results showed that the vegetation mainly consisted of forest and tree-shrub mixture in 1990 and 2011. Compared to forest and tree-shrub mixture, the areas covered by grass-shrub mixture and grass were small. The forest cover over dolomite bedrock was higher than that over limestone bedrock, while the grass and grass-shrub mixture covers over dolomite bedrock were lower than those over limestone bedrock. Steady forest cover existed in the areas with limestone and dolomite bedrock regions. In regions characterized by dolomite bedrock, the steady forest cover was higher than that in limestone, and the tree-shrub mixture cover increased slowly in both regions. Grass, grass-shrub mixture, shrub, and tree-shrub mixture vegetation-types were all in the period of positive succession and the percentages of positive succession of these four cases over dolomitic bedrock were higher than that in the areas with limestone bedrock. The connectivity was increased and the fragmentation was decreased in areas with limestone and dolomite bedrock. While, the level of fragmentation and diversity was lower in case of dolomite bedrock than that in case of limestone bedrock. The underlying mechanisms include varying soil depth, soil chemical properties, hydrology, etc. between the two types of bedrocks. The results implied that for grass-shrub mixture and shrub, natural recovery may be more suitable in areas with dolomite bedrock than in areas with limestone bedrock.