This study explores the significant changes of the gender gap, regional divide, and family size effect in the context of intergenerational education improvement and social mobility after the launch of China's reform and open-up policy. The reform and open-up policy, initiated in 1978 China, introduced significant social changes including increased urbanization, changes in family structure, shifts in social norms and values. This study will contribute valuable insights into how such large-scale national policy shape and affect social structures and patterns of mobility among different groups of population, and either reinforce or mitigate forms of social inequality. Therefore, intergenerational education improvement and social mobility are the main focuses as well as key indicators in this study to measure the prevalence, magnitude and changes of the gender gap, regional disparities, and family size effect. This study utilizes data from the China Family Panel Studies (CFPS), a nationally representative, longitudinal household survey of over 14,000 families in contemporary China, and mainly multi-linear regression models with interactive effects to investigate the impact of the reform and opening policy. The results of this study indicates that while there are still social inequality and differences among different population groups in modern China, these differences to some extent have been effectively and significantly reduced over time with the influence of the reform and opening policy.