This research use efficiency with DEA method to calculate the performance of the banks after merger and acquisition. Measurement of efficiency was calculate by historic data starting year 1998 when the regional crisis economic till 2009 after crisis financial global economic in Indonesia. The efficiency ratio has calculated between 0 to 100 percent of the efficiency parameter. The result of efficiency research shows that m & a not significance to increase the efficiently and depends with the qualitative variable of the banks, such: organizational effectiveness and managerial capability. The result of research show that Bank Mandiri has stable efficiency ratio after m & a till 2009 and not influence by the crisis but has significance influence to the efficiency of the peer-groups of the banks. Crisis financial global in the year 2008 only influence Bank Century as a fact. Research also show that only the banks with the capital up to IDR 10 Trillion (+/- USD. 1 Billions) has influence the efficiency criteria of their peer groups of the banks, the capital less than the amount not significance influence the efficiency criteria of their peer-groups. Efficiency ratio measure by DEA method and analysis, tests of efficiency before and after m&a using mann-whitney test non parametric approach with abnormal data distributions, analysis of peer groups influence by m & a measure with ANOVA tests and analysis of influence financial crisis global in year 2008 measure by pair-wise method the efficiency ratio before and after crisis.