A multi-agent-based urban power grid isolated island black-start system and method belongs to the field of operation control of power system field. A plurality of units which can achieve splitting isolated island operation are configured in main power plants in advance, the units are required to be capable of supplying first-class and second-class loads or providing start capacity of other power plants after undertaking auxiliary power load and can guarantee stable operation of auxiliary powers after emergency load shedding; when a power grid system suffers from large disturbance or has a major fault, transformer substation monitoring agents of an affected area and power plant monitoring agents can actively split into isolated island operation states, when the fault is finally evolved into a blackout, all the stable-operation power plant stage and transformer station stage isolated islands in the power grid report respective isolated island operation conditions to a power grid monitoring center agents. The multi-agent-based urban power grid isolated island black-start system and method can greatly shorten power grid black-start time and reduces economic losses and social influences caused by the blackout.