This paper explores the reasons and process of the social changes in the Soviet Union and Eastern Europe through an empirical study on social transformation in the Soviet Union and Eastern Europe from a perspective of social structure stratification. First, changes in social structure both in urban and rural areas caused by a high degree of industrialization and urbanization is the basic reason for social transformation in the Soviet Union and Eastern Europe, which is an aspect of relevance in social transformation between them and East Asia, Latin America and other countries or regions. And the complex flow system and structural stratification caused by migration flow into cities has a direct impact on the social transition of the Soviet Union and Eastern Europe. The middle class, especially its values, social functions and political attitudes has had a significant influence on the radical system transformation and this impact should not be underestimated. Secondly, the specific process of transition in the Soviet Union and Eastern Europe can be clearly divided into two phases: first stage is deep-level changes in social structure, namely, the changes of class stratification from peasants to urban workers; second stage is the surface-level changes in social structure, namely, class stratification because of diverse interest under the background of marketisation.