Abstract: Based on the higher-order-zigzag theory (HOZT) and the assumption of nonlinear transverse displacement over the entire core thickness, the Finite Element Method (FEM) was utilized to analyze three Composite Sandwich Panels (CSPs) produced by the vacuum import process. The CSPs included a wood core-Glass-Fiber-Reinforced-Polymer (GFRP) sheet, a wood core-GFRP sheet combining bamboo reinforcement laminate, and a foam core-GFRP sheet. The stress disparity between interlaminates was proposed to indicate the resin-seam stress state, and the Von. Mises yield criterion was considered as a denotation for ultimate-load calculation at some special spots. Owing to the low precision of the CSP transverse shear stress acquired by the constitutive relation and the FEM calculated displacement directly, the indirect method with transverse shear stress equilibrium equation and the Least Square Error (LSE) were applied. The analyses show that compared with the results from experiments and the Equivalent Section Method (ESM), FEM is significantly effective and practical in coping with stiff and soft CSPs, hence is suitable for accurate analysis and design of CSPs. On the other hand, the ESM is suitable for relatively stiff-core CSPs and preliminary estimation.