The main objectives of Venetian blind shading system is to obstruct direct sunlight and at the same time allow daylight to penetrate into the room. However, due to the lack of data, design and evaluation tools, it is difficult for building designers to evaluate shading performance of Venetian blinds during the building design stages. The purpose of this study was to develop an analysis method for shading and daylighting effects of Venetian blinds using the RADIANCE program.