Sandwich structures are important structural members in modern lightweight engineering. Accurate and effective buckling predictions are vital to the design and optimization of sandwich structures. This paper extends and validates a homogenization theory namely the mechanics of structure genome (MSG) in predicting eigenvalue buckling of sandwich structures under compressive and bending loads. Global buckling is predicted on a homogeneous plate with effective plate properties computed by MSG. Local buckling is predicted by perturbing the fluctuating function of structure gene under Bloch-periodic boundary conditions. Accuracy of buckling predictions is validated by three-dimensional finite element analysis.