Quality and quantity of rural-urban immigration and the emergence and expansion of informal settings,, to much extent,,, are two faces of the coin of the kind of development in developing societies and regions. One of the ways to describe and explain these two phenomena is to analyze their temporal and spatial relationship in the historical process from the point of view of the people who have been involved in the phenomenon of migration and living in these settlements. The current research has analyzed the trend and driving factors of immigrants' migration to the informal settlement of Madewan city with aid of grounded theory as a qualitative methodology. The participants in the research were 30 residents of this city who were selected based on the non-random and purposeful sampling method. For data collection and analysis, the semi-structured individual interview method and Strauss and Corbin's three-stages open, central, and selective coding method were selected, respectively. Based on analyzing the data, we can describe and analyze the trend and related factors of the immigrant, s immigration to this city under three different stages “Self-sufficiency and not thinking about immigration"; " Objective-subjective contexts driving to and awareness of migration"; and "decision into and tone practical action to migration and its escalation”. As a result, it can be said that the temporal-rhythmical variety of immigration into Madovan and its related factors are different and multiple in that before the 70s there was little and almost zero immigration, in the 70s there was a kind of limited-individual immigration and in the 80s an intensified and collective kind of immigration has occurred in this area.