The purpose of this study is to explore the impact of operating risk and cost on Taiwan's Banks joining Financial Holding Company, under the assumption of oligopoly and risk-adjusted. The empirical results show: (1) the price of financial stocks, scale, book-to-market ratio, and momentum are important factors of banks' stock price. Beta value will approach to 1 when Taiwan's Banks join Financial Holding Company. (2) The cost saving of Taiwan's Banks join Financial Holding Company is 9.84%~13.82%. (3) Taiwan's Banks join Financial Holding Company can decrease operating risk.