This essay explores the business performances' difference between prior-merger and post-merger of acquiring banks. We select the fifteen variables from five financial indexes on the three years before and after acquiring banks go into a merger to examine the business performance of post-merger of acquiring banks through samples matched T test. Our findings indicate the business performance of post-merger of acquiring banks is not different significantly. We are also no evidences to support the business performances' difference between each year of post-merger and prior-merger of acquiring banks.