A bandwidth scheduling method performed by a bandwidth allocation apparatus, wherein the method comprises: receiving, by the bandwidth allocation apparatus, a bandwidth request message sent by a message conversion apparatus, wherein the bandwidth request message comprises a bandwidth requirement, and the bandwidth requirement is a bandwidth used for completing transmission of a service; calculating, by the bandwidth allocation apparatus, first bandwidth grant information and second bandwidth grant information based on the bandwidth requirement, wherein the first bandwidth grant information is information about a bandwidth that is allocated to a user-side device and that corresponds to the service, and the second bandwidth grant information is information about a bandwidth that is allocated to a second access device and that corresponds to the service; and sending, by the bandwidth allocation apparatus, a first bandwidth response message to the message conversion apparatus, and sending a second bandwidth response message to a first access device, wherein the first bandwidth response message comprises the first bandwidth grant information, and the second bandwidth response message comprises the second bandwidth grant information, wherein the first access device is an optical line terminal, OLT, the second access device is an optical network unit, ONU, the message conversion apparatus is disposed on or outside the second access device, and when the message conversion apparatus is disposed outside the second access device, the message conversion apparatus receives and sends a respective bandwidth request message and a respective bandwidth response message by using a protocol between the message conversion apparatus and the second access device. receiving, by the bandwidth allocation apparatus, a bandwidth request message sent by a message conversion apparatus, wherein the bandwidth request message comprises a bandwidth requirement, and the bandwidth requirement is a bandwidth used for completing transmission of a service; calculating, by the bandwidth allocation apparatus, first bandwidth grant information and second bandwidth grant information based on the bandwidth requirement, wherein the first bandwidth grant information is information about a bandwidth that is allocated to a user-side device and that corresponds to the service, and the second bandwidth grant information is information about a bandwidth that is allocated to a second access device and that corresponds to the service; and sending, by the bandwidth allocation apparatus, a first bandwidth response message to the message conversion apparatus, and sending a second bandwidth response message to a first access device, wherein the first bandwidth response message comprises the first bandwidth grant information, and the second bandwidth response message comprises the second bandwidth grant information, wherein the first access device is an optical line terminal, OLT, the second access device is an optical network unit, ONU, the message conversion apparatus is disposed on or outside the second access device, and when the message conversion apparatus is disposed outside the second access device, the message conversion apparatus receives and sends a respective bandwidth request message and a respective bandwidth response message by using a protocol between the message conversion apparatus and the second access device.