With the increase of installation of wind energy in power systems, it has become a great challenge to evaluate the maximum wind energy limit penetration of a given regional power grid. By analyzing the self-organized criticality of complex power systems, a method based on interval Optimal Power Flow (OPF) cascading failure model to evaluate the maximum wind penetration is proposed. This method models the wind power output uncertainty as an interval number to form the interval cascading failure model based on interval OPF of power grids. With the increasing wind power penetration, the rules between the probability and scale of cascading failures can be discovered. The maximum wind power penetration is determined by the average of wind power when the power grid exhibits the self-organized criticality. Simulation experiments on IEEE 30-bus system and IEEE 118-bus system verify that the proposed method is a reasonable quantitative measurement method for assessing the wind power penetration limit of a power system. This work is supported by National Natural Science Foundation of China (No. 51507056).