Abstract: Taking an isolated power grid at a certain industrial park as example, simulated analyses are done on the stability of the power grid the connection of the smart nuclear power plant, which simulates the scenarios of "N-1" falts of nuclear power units and three-phase short circuit faults at the outgoing lines of nuclear power units. It is suggested to take comprehensive measures of increasing system rotation reserve capacity, distributed accessing of nuclear power units, and improving the action time of protection equipment after the connection of small nuclear unit to the isolated small grid.