This paper has performed a test and analysis study on the woven glass and carbon fabric/epoxy laminate composite and sandwich panels of mid-size bus vehicle. Mechanical properties of core and composite materials are needed for accurate analysis of the sandwich composites. Elastic and shear modulus and poisson"s ratio of GFRP and CFRP and core material were established from the tension, shear and bending specimens test. Also, fatigue strength Se is established from the fatigue test using the stair case method that one of the statistical method. The fatigue test was conducted using a tension-tension load with a stress ratio R of 0.1 and frequency of 10 Hz. In order to do FE model verification and evaluate the structural behavior and safety of the joint structure of side panel, the static load tests such as vertical load and compressive load and torsion load tests have been conducted. Finally we achieve a lighter mid-bus structure satisfying the target stiffness, strength and durability, and this technique will be applicable to other vehicles and components.