Because of its long term civilization history, Iranian traditional architecture has seen a great amount of daylighting experiences, including 6 daylighting systems with 26 kinds of wall and ceiling windows. In this regard it has some valuable lessons to give to architectural community. Using field data collection and computer simulation, this article tries to find out the distribution and diversity of daylight in traditional houses to give some recommendation to contemporary architecture of Iran. To achieve this aim, “Ameri House Complex” in Kashan with 7 yards, 85 rooms in different sizes such as “3-door room”, “5-door room”, “7-door room” and halls located in north, south, south east and south west directions, has been chosen as a case study. In two days during spring and summer of 2011, and winter of 2012 the field study was performed to gather daylight data from 14 different chosen rooms of this house. A digital Lux meter data logger was used to gather the illumination data on the roof as the reference point. The exact size, dimension and the ceiling shape of each room were measured. Other properties of each room such as its location in the House and geographic orientation, its place in the yard, the location of the window in the room wall, ratio of the window area to the room area, ratio of the window glazed area to the frame area, and other details such as the materials, colors and shapes of the frame and glazed part of the window were recorded. Subsequently, using the criteria and calculating methods introduced in handbooks of lighting and daylighting, all the information were analyzed in four steps: 1- Room specification. 2- Geometry and neighborhood condition. 3- Analyzing the field data. 4- The illumination condition of each room in a whole year was simulated using Radiance Software. The results show the relationship between shape and condition of windows and space with interior daylighting distribution and quantity. These principles will be useful for architects to improve daylighting design in modern buildings.