Securities underwriting refers to the behavior of securities companies issuing securities on behalf of securities issuers. Securities underwriting business can be commissioned or underwritten. Among them, securities underwriting refers to the underwriting method in which a securities company purchases all the issuer's securities according to the agreement or purchases all the after-sales securities by itself at the end of the underwriting period; Securities consignment refers to the underwriting method in which securities companies sell securities on behalf of issuers and return all unsold securities to issuers at the end of the underwriting period.