A method for online switching of an operation mode of an ONT comprises: receiving an OMCI message in an online state by the ONT, wherein the OMCI message carries an indication message for switching the operation mode; and switching the operation mode according to the indication message by the ONT. The above-mentioned method realizes changing of an operation mode of an ONT in real-time in an online state based on the GPON standard, so that the ONT can flexibly operate in a gateway mode or a network bridge mode, and an operator management system only needs to change the operation mode of the ONT through a standard OMCI message according to a local network requirement.