The invention discloses a method for identifying key equipment of wind power access system based on decision tree. The method comprises: through calculating probability and blackout scale of certain times of cascading failure, confirming the target threshold value of the VaR index, and then recursively creating the simulation data of the certain times of cascading failure into decision tree and analyzing; screening leaf node which meets the requirements and selecting an attribute variable on path of where leaf nodes locate as the pending key attribute variable, with the corresponding control equipment as the pending key attribute equipment; through pending key attribute equipment, reducing the appearance probability of pending key attribute variable on the path; conduct blackout risk assessment on controlled system, if the risk index meets requirement, the control and simulation is finished, and the attribute variable is proved to be key equipment. Adopting the method can analyze other blackout factors aparting from the system transmission circuit and the 'key fault set' can be obtained from the analysis. The method is applicable for power system with wind farm.