This paper describes a method for measurement and analysis of surface reflection properties of water paints under a variety of conditions. First, a gonio-spectro photometer is used for measuring the radiance factor of a painting surface at different incidence and viewing angles. Then, we analyze the reflection properties of water paint. A 3D light reflection model is derived based on the Torrance-Sparrow model and the Oren-Nayar model. An algorithm is presented for determining the model parameters including specular coefficient, diffuse roughness, specular roughness, refractive index from the observed spectral reflectance data. Finally, we show the validity of the proposed model in experiments and render color images of water-painted objects by using the estimated parameters.