3D object models are becoming widely used for computer graphic rendering or virtual environments. For rendering a 3D object, an object model is constructed from 3D spatial data by 3D system and then combined with several color images from different viewpoint using an optimal texture mapping. However, the discontinuity phenomena are generated somewhere between the merged images. A method of seamless processing for merging color textures of 3D object models is proposed. By transferring the color images from RGB color space to a different one, it separates the brightness from the color information. The seams are smoothed based on the brightness, and the result images are transferred back to the RGB color space. It keeps the color unchanged and maintains the detailed information of textures.