The invention discloses a benders decomposition based droop control island micro-grid power flow calculation method. The method includes: decomposing island micro-grid power flow calculation into a conventional power flow calculation sub problem and a droop node update sub problem, equalizing droop nodes, and initializing the droop nodes; updating loads and line impedance parameters on the basis of the system angular frequency; solving relevant variable parameters of a droop node as a balancing node and droop nodes as PV nodes through the conventional power flow calculation sub problem; determining if the algorithm is convergent or not through a difference between a first iteration state variable and a second iteration state variable of the system; stopping iteration and acquiring a final power flow solution if so; modifying or solving relevant change parameters of the droop node as the balancing node and the droop nodes as the PV nodes through the droop node update sub problem if not; and performing alternative iteration in this way, and acquiring a final power flow solution. The method can lower the solution difficulty of an original problem, accelerate the solution speed, and greatly reduce calculation and the programming difficulty.