This study mainly discusses the effect, in country level, of minority shareholder protection on shareholder wealth during mergers and acquisitions (M&A). In particular, based on the index of anti-director rights (ADRI) developed by LLSV (1998) and the index of shareholder protection index (SPI) by John Armour et al.(2009), I empirically examine the linkage between M&A activities and indexes as well as the components of these indexes. This study expects the result may show some relevance between of indices and M&A activities, and the legal value of this relevance. The purpose is to show whether minority shareholder protection is workable in M&A activities, and whether it can facilitate M&A markets. To begin with, this paper discusses LLSV¡¦s uniqueness in corporate law study ¡V using empirical method to value whether corporate law matters or not around the world. Then, I analyze LLSV¡¦s possible defects, review criticisms and effects they had incurred. Secondly, we design a study to compare the revised LLSV methodology developed by the Harvard scholar Spamann with SPI index through stock market and M&A market. I also code China¡¦s and Taiwan¡¦s data to make up the lack of samples of cross level variation, and take this as the basis for corporate institutional comparison. This study reports that each of sub-indexes from ADRI and SPI has different relevance to M&A activities: three are positive, five are negative, three are insignificant, and two are valueless of discussion (definition or design defect). Thus we may see the importance of law quantification. We appreciate further research and authorities¡¦ consideration following our work in Taiwan. Finally, the contribution of this study is to attempt to integrate empirical and comparative legal analysis, in response to global corporate governance issues of promoting cross research. On policy implications is that it can predict some investor protection mattes, direct the way of policy adjustment. Besides, this study can also suggest specific amendment for Company Law and Securities law to re-examine how to balance between market development and the protection of minority shareholders.