The invention discloses a power system hierarchical parallel decomposition load flow calculation method and device based on graphic calculation. The power system hierarchical parallel decomposition load flow calculation method based on graphic calculation includes the following steps: generating a deltree of a graph data model of the power system, wherein the graph data model connects an undirected graph established by a matrix according to nodes of the power system; according to the deltree, performing parallel hierarchy on the nodes in the graph data model to obtain a plurality of node layers; and performing load flow calculation on the hierarchical graph data model to obtain a load flow calculation result. Since graph calculation based on the graph data model has the advantage that calculation and network communication do not need ordering or synchronization in advance and all the nodes in the graph data model have the characteristic of parallel calculation, when the load flow calculation is performed on the graph data model layer by layer, all the nodes in each node layer and the edges between the adjacent two node layers can perform parallel calculation, thus reducing the timerequired for load flow calculation for the power system.