Herd behavior in financial market is a special irrational behavior, which refers to the behavior that investors are influenced by other investors, imitate other people's decisions, or rely too much on public opinion (that is, the overwhelming concept in the market) without considering their own information under uncertain information environment. Herding behavior involves the related behaviors of multiple investors, which has a great influence on the stability and efficiency of the market and is also closely related to the financial crisis. Therefore, herding behavior has aroused widespread concern in academic circles and government supervision departments. Herding behavior refers to animals (cattle, sheep and other livestock) moving in groups and foraging. Later, this concept was extended to describe the phenomenon of human society, which means thinking, feeling and acting like most people, being with most people and being consistent with most people. Later, this concept was borrowed by financial economists to describe an irrational behavior in financial markets, that is, investors tend to ignore their valuable private information and follow the decision-making methods of most people in the market. Herd behavior refers to that a large number of investors adopt the same investment strategy or have the same preference for specific assets in a certain period of time. Since 1980s, more and more attention has been paid to the study of herding behavior, which was once considered irrational and unscientific by traditional finance. Herd behavior can also be called group psychology, social pressure, infection and so on. Especially in recent 10 years, with the deepening of people's understanding of the nature of financial markets and the in-depth thinking of investors' behavior caused by frequent financial crises, the research on herding behavior in financial markets has become a very challenging and practical direction. Asch was the first psychologist to study group behavior. 1952, he conducted an experiment among American college students and found an irrational herd behavior. He called this kind of behavior the same kind of pressure phenomenon. He let the real subjects enter a new class and let the others in the class answer a very simple question first (the comparison of the lengths of two line segments). These people were told to give wrong answers on purpose, and finally the subjects answered. Results 1/3 subjects were affected by the wrong answer. In the case of independent answer, the possibility of wrong answer is almost non-existent. A great deal of evidence from the financial market shows that participating in herding behavior is not good for the main body, and the investment individuals who actively participate in herding behavior get lower returns in the market. At the same time, there is a positive feedback mechanism between herding behavior and stock price fluctuation, which makes many scholars think that herding behavior is an important factor leading to excessive market price fluctuation. In the study of the recent financial crisis in Southeast Asia, we found that the herding behavior of foreign investors contributed to the financial crisis. Therefore, herding behavior has aroused widespread concern in academic circles and government supervision departments. Therefore, the existence of irrational herding behavior is unfavorable to both individuals and the whole market. In order to control this irrational behavior, it is necessary to study the causes of herd behavior. Only by deeply understanding the causes of herd behavior can we find the right medicine and the corresponding control methods. A: Individual investors in China stock market show very obvious herding behavior, and the herding behavior of sellers is stronger than that of buyers. Time factor has no significant influence on investors' herding behavior, and investors' herding behavior stems from its internal psychological factors. B. In different market situations, investors show significant herding effect, that is, whether investors are risk-averse or risk-averse, they all show significant herding effect. C. Stock return rate is an important factor affecting investors' herding behavior. When the stock rises on the trading day, investors show stronger herding behavior. On the trading day, the herding behavior of investors and buyers is greater when the stock falls than when it rises, while the herding behavior of sellers is the opposite. Generally speaking, the seller's herd behavior is greater than that of the buyer. Stock size is another important factor that affects investors' herding behavior. With the decrease of circulating share capital, the herding behavior of investors gradually increases, which is consistent with the conclusion of foreign scholars.