To compete globally, the financial service industry in Taiwan continuously expands markets and integrates sources and is one of the industries popular in mergers and acquisitions lately. Counting on people to deliver service is one of the traits in the field, therefore, it¡¦s worthy of attentions and discovery about the relations of the acculturation/the employees¡¦ working attitude/the perceived organizational performance between the acquiring and the acquired firms when combined. The study targets on the two cases of M&As in the financial service industry happened in the past two years in Taiwan and it is conducted by the questionnaire survey. Throughout interviewing total 364 of the staffs and agents in Kaohsiung of two pairs of the acquiring and the acquired companies which were combined, the datum of the research is made by reliability analysis, descriptive analysis, Pearson correlation analysis, independent sample t-test, ANOVA, and multiple regression analysis to analyze the dimensions of the organizational culture and the employees¡¦ working attitudes and the perceived organizational performance of the acquiring and the acquired firms. The major findings are as follows: 1. The Organizational culture and the employees¡¦ working attitude both are statistically significant correlated to the perceived organizational performance, especially the latter affects the perceived organizational performance more than the former does. 2. Among the sub-dimensions, the organizational commitment in the employees¡¦ working attitude explains most the variation of the perceived organizational performance and then the recognition. Also, the service quality in the organizational culture explains most the one. It means that the organizational commitment and the recognition of employees¡¦ as well as the service quality are with significant influences on the perceived organizational performance. 3. The Organizational culture is statistically significant correlated to the employees¡¦ working attitude, and among its sub-dimensions the service quality explains most the variation of the employees¡¦ working attitude and then the teamwork. In other words, the service quality affects the working attitude of employees¡¦ significantly. 4. The working attitude of the employees¡¦ of the acquiring firm A is significantly different from the one of the acquired firm B, however, the odds in the identity degrees of the organizational culture and the perceived organizational performance between A and B are no significant. 5. The variations in the identity degrees either of the organizational culture, the working attitude of employees¡¦, or the perceived organizational performance between the acquiring firm C and the acquired one D are significant. The research gives the evidence that the working attitude of employees¡¦ affects the perceived organizational performance most. It represents that the acquiring firms should pay more attentions to the soft integration such as human resources and culture when combined to know better the expectation and to reduce the uncertainty of employees¡¦ of both the acquiring and the acquired, to enhance the strength and value identified by both sides in order to reinforce the confidence as well as the identity of the employees¡¦ if it wants the merger to reach the expected accomplishment.