In computer graphics, for realizing realistic rendering, it is very important issue to set surface reflectance parameters accurately when surface atturibute modelling. So far, these parameters are established without taking no account of real objects, so that the reality of surface characteristics is lacked in generated images. This paper describes a method for measuring surface reflectance parameters of an object by image sensing. The intensity distribution are taken from brightness images while rotating a target object or while moving of light sources. The surface parameters including specularity are obtained by an iterative least square fitting. After the fitting process, it is possible to generate realistic objects by the correct surface parameters based of the phyisics-based measurement. Although experimental generated images are not accurate in phyisics sense, they is feasible for computer graphics.