Urban system is an agglomerations of towns and cities related together and created structure of urban settlements in a region or a country. One of the most aspects of urban system is spatial distribution of population. Whereas, spatial distribution in the urban system is affected by different factors and also it can affect socio-economical and management factors; so it is required to study more exactly. Studies show that in Iran in 1279 Hijri, urban system has had homogenity and it has continued to 1335, but after this decade, relationship between rural, towns and cities disrupted and inequality increased. In the present paper, several quantities models like urban primacy, concentration, and equality models used to study change trend of urban system from 1335 to 1385 hijri and to evaluate effects of applied policies for balance. Concluded results show that inequality and unbalance increased in spatial distribution of population in Iran urban system until 1335. But after this decade up to now, equality in spatial distribution is increasing and urban system going to appropriate and balanced form.