From the beginning of the 1960’s to 2013，Latin America achieved the triple-jump of the urbanization. Between 1950 and 2000，the number of cities with population over 20 000 increased by almost 8 times. As a result of the urbanization process，the region realized an economic transformation with two features. First，the level of urbanization continued to be higher than that of economic development. “Over-urbanization” and “Middle-income Trap” are two major phenomena. The stagnated industrialization and the suppressed household consumption are the basic reasons for them. Second，there emerged the rural economic sector，the foreign capital economic sector，the formal economic sector of urban area，and the informal economic sector of urban area. On the whole，the social transformation in the region has two main characters. First，two social relations （based on community and profession respectively） and three social classes （elite，formal and informal） got concreted. The social fragmentation is a special phenomenon in Latin America. The community-based social relation and the profession-based social relation have horizontal and vertical impacts on fragmentation respectively. As a result of the three social classes，the social structure in the region is pyramidal. Second，there has existed the contradiction between state and society. Some Latin American countries have been practicing the “3-pillars” frame of social cohesion and social management. As for the political transformation，the region has finished the process of transforming from populist politics to party politics. In the process of political transformation，the region witnessed the internationalization of economy，the differentiation of interest groups，the stratification of society，the solidification of political elite，and the socialization of government. The article summarizes one basic frame for observing and investigating Latin American countries，which is “12345”. “1” represents one contradiction，which is the contradiction between state and society. “2” represents two social relations，including the community-based and the profession-based social relations. “3” represents three social classes，which are the elite，formal and informal classes. “4” represents four economic sectors，which are the rural economic sector，the foreign capital economic sector，the formal economic sector of urban area，the informal economic sector of urban area. “5” represents five “actions”，which are the internationalization of economy，the differentiation of interest groups，the stratification of society，the solidification of political elite，and the socialization of government.