The invention belongs to the technical field of power grid reactive voltage optimal control raining, and particularly relates to a power grid reactive voltage self-adaptive dynamic partitioning methodbased on secondary voltage control. The method comprises the steps: determining requirements to be met by power grid partitions; establishing a full-dimensional voltage/reactive sensitivity matrix containing PQ and PV nodes in a successive recursion mode; on the basis of a community structure theory, in order to accurately describe the coupling degree between nodes on the basis of original modularity function definition, expressing the weights of edges between the nodes by voltage/reactive sensitivity; starting from the controllability of a reactive power source, mapping a load node to a reactive power source node with the maximum voltage/reactive power sensitivity to complete initial partitioning; and combining the initial partitions by taking the maximum modularity function value as a measurement index, and automatically determining the number of the partitions to form an optimal partition. Complexity of partition calculation can be reduced, partition efficiency is improved, electrical strong coupling of nodes in a region and electrical weak coupling of nodes in the region are guaranteed, the number of partitions is automatically determined, and self-adaption dynamic partition is achieved.