Several factors can affect the received power of solar collectors which among them, the solar collector angle can be determined by the users. So in this paper, general models for optimum tilt angles are proposed for Solar Hejri (SH) months that which are applicable for all of iranian cities. Obtained models are a function of SH day number and latitude and the optimum tilt angles can be calculated only by SH day number and latitude in each point of iran. In order to examine the validity of proposed model, the obtained results are compared with other literatures.