Statistic samples of this paper are M&A transactions of listed family enterprises of pharmaceutical manufacturing industry from 2011 to 2013. Earnings conservatism and M&A performance of the enterprise are respectively measured by event study method and KW model.It is analyzed that earnings conservatism has effects on M&A performance of family enterprise through financing contraint and agency problem. The study shows that earnings conservatism of family enterprise is rather weak, and there is a positive correlation between earnings conservatism and the short-term M＆A performance，but no significant relationship between earnings conservatism and the long-term M&A performance．