This paper explores the impact of differences of corporate culture and human resource management before and after merger on employees' organizational commitment. Through in-depth interview and survey of a domestic bank holding company, 324 effective questionnaires are analyzed by multiple regression analysis in this study. Empirical findings indicate that differences of corporate values & norms and rules & regulations before and after merger have a significant influence on employees' organizational commitment. As for human resource management, members' organizational commitment will be significantly influenced by differences of corporate's training & development and performance assessment before and after their merger.