Synergy effect refers to that the benefit after merger is greater than the sum of the benefit of the first two companies, that is to say, the growth of the company's performance after merger is greater than the sum of the expected growth of the performance of the original merger and acquisition parties, focusing on the contribution of the merger and acquisition behavior to the enterprise, in line with the principle of maximizing the value of the enterprise, and able to integrate the merger and acquisition behavior with the investment concept. Synergy can be divided into three forms: management, finance and operation. This effect has the following characteristics: scale economy, reducing transaction costs, scope economy.