Google merged Youtube, Microsoft wants to merge Yahoo to compete. ACER declared in October 2007 that it merged the fourth largest computer manufacturer in US: Gateway. Above are the representatives of big merger and acquisition cases. Enterprises grow up through M&A is a trend recently, but are all the M&A cases bringing positive performances? The answer is negative. We can prove that through the cases of BENQ-Siemens and Acer-Counter Point which all ends in failure. Therefore this research reviewed related literatures and focused on the cases that serve Taiwan enterprises as the merger & acquirer between 1997 and 2006. In order to examine whether M&A experiences, types and acquirer¡¦s slack will affect M&A performance or not and to find out whether the factors affecting Taiwan enterprises to conduct M&A are the same with overseas firms or not. This research used multiple-regression model which have five independent variables ¡V M&A times, types, debt ratio, FCF ratio and sale scale. On the other hand, this research utilized 3 dependent variables to compare different point of view on performance, they are unit employee output value, return of total assets and income after taxes. The results show that the hypothesis that M&A experiences and types will have significant impact on M&A performance is rejected. On acquirer¡¦s slack, only sale scope has significant impact on M&A performance. When serving ROA as dependent variable, FCF ratio has significant impact, while others possess insignificant loadings. These results told us that the factors of M&A behaviors in Taiwan are different from overseas firms.