At present, we are in the situation of economic globalization and continuous improvement of market economy system. If an enterprise wants to develop for a long time, it must have M & A activities. Although M & A can bring economic benefits to enterprises, it has advantages and disadvantages to do anything. M & A is a kind of investment activity, the process of investment will be accompanied by risks. And the risk runs through the whole process of M & A, the biggest risk is financial risk. Therefore, we have to pay attention to the financial risk management of M & A, and take a series of measures to reduce the loss of financial risk to enterprises. This paper mainly studies the knowledge of enterprise merger and acquisition, and focuses on two aspects: the first is the financial risk that the enterprise will encounter when it conducts merger and acquisition; the second is how to deal with the financial risk in the process of merger and acquisition. The first section introduces the practical significance, practical theory, research purpose and research results of enterprise merger and acquisition in China; the second section introduces the definition, motivation and significance of enterprise merger and acquisition, as well as the concept of financial risk; the third section introduces the financial risk of enterprise merger and acquisition due to information asymmetry, price, fund raising, fund settlement, management and other issues; It also introduces the sources of these problems in many aspects. The fourth section introduces the financial risks that enterprises encounter in M & A and how to prevent them. The last part is about the conclusion that I got from the study of M & A in this paper.