Using dimensional analysis and experimental technique, the aero-optical effect at the second stage of a compressible mixing layer has been investigated. The theoretical analysis focuses on the relation between two-dimensional large-scale structure of a mixing layer and its corresponding aero-optical effects. Results show that the time-averaged bore-sight error (BSE) has nonlinear variability with the convective Mach number (Mc). Moreover, we also present the relation among time-averaged BSE and turbulent kinetic energy, Reynolds shear stress at the interface between the mixing layer and free stream. Experimental results from a thin beam light passing through the compressible mixing layer verifly the theoretical result between time-averaged BSE and Mc.