Abstract: The dissolution operation is a common operation in patch generalization and it involves a large number of computations. Due to limitations in computational power, it is very difficult to process a large number of patches over a large area using traditional dissolution methods. To overcome this limitation, this paper proposes a partitioned dissolution method for long and narrow patches (LN patches) by introducing the block strategy and focusing on the topological changes that occur in the partition lines of LN patches at partition-cell boundaries. Firstly, the topological changes that appear around partition-cell boundaries during the dissolution of LN patches are summarized into four patterns. For each of these patterns, a corresponding method is formulated for reconciling the topological changes of the partition line. Our approach is then validated by using the national geographical conditions data of Chishui City, Guizhou Province. It is experimentally demonstrated that our method is capable of processing large-scale patch data and greatly improves the efficiency of patch dissolution opera-tions. The results of our partitioned dissolution method are also found to be strongly consistent with the unpartitioned method of dissolution. Our method is therefore viable for practical applications.