Abstract: In this paper, moisture absorption characteristics of Carbon/Glass and Carbon/Aramid hybrid composites with bo types of matrices are investigated. The weight gain of the specimens are tested at 80℃. It is found that the water diffusion in hybrid composites can be described by Fickian process. The Step-by-step model and new thermal model are developed to estimate the equilibrium moisture content (Mm) and water diffusion coefficient (D) in hybrid composites using the hybrid structure parameters (hybrid ratio and hybrid intedece number). The estimated values are in good agreement with the experimental results.