In view of the voltage fluctuations and power flow returns caused by large-scale distributed power grid-connection, the research on the group control strategy of distributed power is an important work for the construction of novel power system to ensure its safe and stable operation. In this paper, the observable controllability of distributed photovoltaic grid-connection is analyzed, and a distributed photovoltaic layer control strategy based on cloud-cluster-end architecture is proposed, with cluster as the middle layer. The cloud control center integrates and analyzes the uploaded operation data of each cluster, selects the dominant node which can sensitively reflect the voltage change of the cluster, and constructs a coordinated optimization strategy among the clusters with the goal of no overrun of the node voltage in the whole region and minimal network loss in the system. Cluster layer control platform analyzes the operation data, load information and reactive power compensation device monitoring data uploaded by the terminal device layer, so as to achieve the safe operation of node voltage within the cluster, the minimum network loss of the cluster and the maximum in-place absorption of distributed photovoltaic cells, and constructs an optimal control strategy within the cluster. Finally, the safe operation of node voltage in IEEE 33-node system, over-limit and other typical scenarios are optimized and controlled by the proposed distributed power group control optimization strategy. The results show that the proposed control strategy can effectively solve the over-limit voltage problem, reduce the node voltage deviation and system network loss, and ensure the safe and economic operation of the system.