Disclosed is an optimal power flow-based hierarchical control method for a distributed energy storage system (ESS), where the method divides control of an energy storage cluster into three layers, performs primary and secondary control to realize intra-cluster control, and performs tertiary control to realize inter-cluster control. In the primary control, droop coefficients are set to realize intra-cluster basic power distribution. In the secondary control, a frequency/voltage shift and uneven power distribution that are caused by a droop are compensated for based on a consistency algorithm. In the tertiary control, a central controller is set, a solution of an optimal power flow is calculated and delivered to each cluster as a control signal, and the control signal is tracked in real time through the secondary control and the primary control. The method adjusts a reference voltage of each energy storage cluster without requiring a common bus.