We examined the deformation behavior of CFRP laminates with delaminations by the buckling analysis based on nonlinear FEM. First, the buckling mode is estimated by linearlized eigenvalue buckling analysis. The result shows that local buckling is generated due to the existing interlaminar delamination in CFRP laminates under compression. Next, we calculated the reflection spectra of FBG sensors embedded at the delaminated region in the laminate, using post-buckling analysis and coupled-mode theory. From the result, we confirmed that the local buckling can be detected by reflection spectrum of the embedded FBG sensor.