Abstract: The paper explains briefly the definition of marginalized district, which refers to the district whose gap is increasingly widened from the core district in the area development. Taking Chizhou City, Anhui Province as an example, the paper analyses its space periphery, i.e. slow development of the district social economy and standing in the bottom of Changjiang Economic Belt; Constant fall of the major \{economic\} indexes in the provincial economic ratio; People's living standard and the level of local administration obviously lagging behind the times; Transport periphery increasing etc. The paper also explores the major mechanisms in the formation of the space marginalized district, which includes the historical factor of slow space process, space factor of the illdeveloped city system, artificial factor of frequent transfer of administrative division and economic factor of primitive industrial structure. The marginalized district has such negative effects on the area social economic development as: the vicious circle between the spaces marginalized district and the area social economic development; instability and disorderly development of space structure.

Key words: marginalized district, features, mechanism of formation