After the 1990s, the activities of acquisition among firms have become an international trend. Associated with the situation of global economic slump, both the domestic and international enterprises are eager to establish more powerful and effective business groups, and strengthen their competitiveness in order to create firms with higher commercial value. The rapid acquisition by firms usually results in the situation of promptly laying off employees, decreasing employees¡¦ salary, etc, and therefore generates many risks to the entire groups. The employees of those enterprises being acquired feel unsafe about their future, so their working pressure keeps growing. Similarly, the employees of the firms that conduct acquisition also worry about their working rights being threatened by the increasing number of competitors brought by the organizational reformation. These negative impacts usually have several effects: e.g. reluctance of working, uncomfortable working atmosphere, loss of human resources, and decrease of firm¡¦s overall productivity. It is found that comparative less literature focuses on exploring the influences of acquisition, and investigate the correlation between its impact and the promise given by firms and employees¡¦ working effectiveness. This study distributed 120 questionnaires in total: 90 returned and 80 effective. First, the construct validity of factor analysis and evaluation and the reliability of Cronbach alpha value were used as the tool of analysis. Then Regression Analysis was also adopted and the conclusions listed below were made: A. After acquisition, the employees¡¦ (those of enterprises being acquired) expected distance has significant negative influence toward organizational promise. 1. After acquisition, the employees¡¦ expected distance has negative influence upon firm¡¦s emotional promise. 2. After acquisition, the employees¡¦ expected distance has negative influence upon firm¡¦s sustained promise. 3. After acquisition, the employees¡¦ expected distance has negative influence upon firm¡¦s moral promise. B. After acquisition, the influence of employees¡¦ (those of enterprises being acquired) expected distance toward their working effectiveness is uncertain. 1. Evaluation of working effectiveness from subjective perspectives: 1.1. After acquisition, the employees¡¦ expected distance has no significant influence upon missionary effectiveness. 1.2. After acquisition, the employees¡¦ expected distance has positive influence upon contextual effectiveness. 2. Evaluation of working effectiveness from both subjective and objective perspectives (only limited to those who have records of subjective working effectiveness): 2.1. After acquisition, the employees¡¦ expected distance has no significant influence upon objective working effectiveness. 2.2. After acquisition, the employees¡¦ expected distance has no significant influence upon subjective missionary effectiveness. 2.3. After acquisition, the employees¡¦ expected distance has no significant influence upon subjective contextual effectiveness.