The invention discloses a micro-grid modular energy storage device optimal configuration and control method. The method comprises the steps that 1) energy storage power is configured; 2) the capacity of an energy storage battery is calculated; 3) the energy storage battery is selected according to an actual energy storage battery type selection principle; 4) during the operation of a micro-grid system, the charge-discharge state and the charge-discharge value of an energy storage system are established according to the output value of each distributed power supply and the conditions of the SOC and SOH of the energy storage battery; and 5) grid-connection and off-grid switching needs to be carried out, a seamless switching mode is used, and specifically off-grid to grid-connection, planned off-grid and unplanned off-grid are seamlessly switched. According to the invention, the method describes a whole set of solutions of an energy storage unit in the micro-grid, and has the characteristics of typicalness, operability and the like.