According to the different responsibilities and risks of investment banks in the underwriting process, underwriting can be divided into three forms: underwriting, best-selling and balanced underwriting. Securities underwriting refers to the behavior that an issuer entrusts a securities operation institution to sell securities to the public. When an issuer publicly issues securities to an unspecified object, it shall be underwritten by a securities company according to law. Securities underwriting business adopts the mode of consignment or underwriting. Securities underwriting is the behavior of securities institutions issuing securities on behalf of securities issuers. It is one of the most basic business activities of securities institutions.