在理论上研究了电磁感应透明（EIT）介质的高阶非线性特性。引入一种区别于迭代法的新方法，该方法基于暗共振的分布情况，得到跃迁密度矩阵元的全解，在此基础上得到原子体系对探针光的各阶响应。研究结果表明，线性（一阶）极化率表现破坏性相干，非线性(三阶)极化率表现建设性相干；在各向同性介质中偶数阶次的非线性响应消失。进一步研究发现，五阶极化率和线性极化率一样呈现破坏性相干。研究结果为探索光波在EIT介质传输过程中高阶非线性对光波演化的影响提供了理论依据。该方法为研究高阶非线性效应提供了一种新的理论途径。

High order nonlinear characteristics of electromagnetically induced transparency (EIT) media are theoretically investigated, and a new theoretical method different from iterative method is introduced based on the distribution of dark resonance and leading to a complete solution for a density matrix element. From the solution, every order response for atoms to the probe field is obtained. It is demonstrated that the linear susceptibility (first order) shows destructive interference while the nonlinear susceptibility (third order) displays instructive interference. The even-order nonlinearity is absent in an isotropic medium. Furthermore, it shows that the fifth order nonlinear susceptibility exhibits destructive interference as the linear susceptibility. These research results provide an theoretical foundation for investigating, for example, the evolution of optical wave under high order nonlinearity in an EIT medium. The new method provides a novel approach for the study of high order nonlinearity.