The connection between coherent structure in turbulence and the aero-optical distortions was studied through proper orthogonal decomposition(POD).The computational fluid dynamics(CFD) solutions of high speed turbulence around a missile IR window were used as resource data.Singular vector decomposition was adopted to achieve POD for the spatial-dependent mean flow field.As optical path difference(OPD) is often used to describe optical performance,the low-order singular value of the refractive index fields has good agreement with OPD caused by the source data.Then a plain method for simulating aero-optical distortions was proposed,in which only singular values of refractive index were used.By using the first order singular value,the method can represent the characters of aberrated wave-front,and the relative error of OPD is no more than 2%.The results also validate the argumentation that most aero-optical distortions are caused by coherent structure.