Abstract Estimated daily solar radiation(Rs) based on climatological parameter measured in the horizontal plane is widely used in various contexts. Economic and technical reasons, it is not possible to measure radiation in all areas and should be based on mathematical models are estimated One of the common methods for estimating solar radiation received by the Earth, the temperature and geographic variables at each location. In this paper a general model for arid and semi arid regions of Iran is estimated to be Rs. In study after study and review of the scientific literature for estimating Rs, the data of solar radiation received by the Earth, (Mj m-2 d-1), temperature, relative air humidity and the daily time scale of the station Tehran, Mashhad and Yazd in central Iran are among the arid and semi-arid. In the period 1350 to 1390 were obtained from the Meteorological Agency. Then, we examined existing data and data-outlier and was excluded by error. In continuation Average data were determined using multiple regression analysis model was calculated by MATLAB software. Based on Statistical Models 2 and 5 elegant model for arid and semi-arid regions of Iran. Moreover, because these two models are latitude solar radiation can be estimated rest of the world, especially in areas with similar latitude to work