The curing stress and deformation of epoxy resin and aramid fiber/epoxy composites was measured using Digital Gradient Sensing (DGS) technique. First, the working principle of the DGS method was explained, and the governing equations were derived based on angular deflections of light rays. Then the angle deflection of light rays due to curing stress of epoxy resin was measured, and the effect of the fiber bundle and aramid fiber fabric on the stress distribution during formation was analyzed. The experimental results show that angular deflections of light rays can be related to nonuniform distribution of curing stress in epoxy. The fiber bundles and fabric style have important effects on the curing stress distribution. These results play an important role for predicting curing stress and deformation of fiber reinforced composites.