The estimation of chlorophyll concentration in the water by use of a field spectroradiometer above the water surface is necessary for the removal of the effect of specular reflection at the water surface. The amount of specular reflection from the water surface was assessed on the basis of the spectral signature data that was measured above and below the water surface. Furthermore, a method to remove the effect of specular reflection from spectral signature data that was measured above water surface was proposed. Finally, chlorophyll-a concentration was estimated accurately from the spectral signature measured by field spectroradiometer above water surface with the proposed surface reflection model.