The invention relates to a control method and control system of an off-network island light storage microgrid. The control method comprises the steps of judging a working mode in which a microgrid system is located according to acquired voltage amplitude of a DC bus; and allocating power between a photovoltaic module and an energy storage battery according to the working mode of the microgrid system. According to the control method and the control system, a converter control mode of the microgrid system is switched by an arbitrary distributed power supply of the microgrid system according to avoltage of the DC bus under different running states on the basis of no interconnection communication mode, the voltage amplitude of the DC bus is used as a judgment reference, the running working condition of the system is judged according to the change quantity of the voltage amplitude, the adjustment of the DC voltage bus is initially participated, meanwhile, power allocation of a system multi-power unit is ensured, so that the system safely and stably runs; and an island microgrid controllable load is mainly a seawater desalination device, the problem of fresh water supply in an island can be solved, and the system is used as an adjustable load for inputting control.