The invention provides a method and a device for judging wind power field cascading off-network failure in a wind power accumulation area. The method comprises the following steps: inputting power grid data and wind power field power-free characteristic parameters; modifying a wind power field outlet bus, and adding a pair of balance capacitive reactance; performing load flow calculation on a modified system; performing low-voltage off-network search on all wind power fields in the wind powder accumulation area once to obtain a first wind power field set with low-voltage off-network; performing high-voltage off-network search on all wind power fields in the wind powder accumulation area once to obtain a second wind power field set with high-voltage off-network; according to the first wind power field set and the second wind power field set, judging a wind power field cascading off-network failure condition in the wind power accumulation area. According to the method disclosed by the invention, power-free characteristics of asynchronous operation of a wind turbine generator in wind power fields and system power-free characteristics after failure is eliminated are simulated through one pair of balance capacitive reactance, so that the wind power field cascading off-network failure condition in the wind power accumulation area can be simulated, the simulated computation amount can be simplified, and the simulated result accuracy is guaranteed.