In this study, the mechanical behavior of composite material system with ultra light weight is investigated in the atmospheric condition. The matrix resin of the composite is epoxy resin and its dispersion is glassy micro "Sirasu Balloon". The composite system developed is a kind of micro porous materials. From the experimental data of bending tests and impact tests, mechanical behavior of the composites was clarified, and the effects of material properties and configurations on the mechanical properties of the composite were discussed from the viewpoint of micro-mechanical study. A homogenization theory with multi-scale analytical method will be described for evaluation of the composite material system in environmental conditions.