A method for measuring a transmission delay of an Optical Transport Network, OTN, device, comprising: generating, by a source OTN device, a delay request frame when receiving a delay measurement request sent by a user, and sending the delay request frame to a destination OTN device; receiving, by the source OTN device, a returned response frame from the destination OTN device, the response frame being generated by the destination OTN device on the basis of the received delay request frame and the response frame comprising first time information, wherein the first time information comprises: system time T1 when the source OTN device sends the delay request frame, time T2 when the destination OTN device receives the delay request frame and system time T3 when the destination OTN device sends the response frame; upon reception of the response frame returned by the destination OTN device, acquiring, by the source OTN device, system time T4 when the source OTN device receives the response frame; and parsing, by the source OTN device, the response frame to obtain the first time information, and calculating a transmission delay between the source OTN device and the destination OTN device according to the system time T4 when the response frame is received and the first time information; wherein the generating, by the source OTN device, the delay request frame when receiving the delay measurement request sent by the user comprises: generating, by the source OTN device, a delay request message when receiving the delay measurement request sent by the user; and filling, by the source OTN device, the delay request message into Optical Channel Payload Unit k, OPUk, of an OTN frame to generate the delay request frame. generating, by a source OTN device, a delay request frame when receiving a delay measurement request sent by a user, and sending the delay request frame to a destination OTN device; receiving, by the source OTN device, a returned response frame from the destination OTN device, the response frame being generated by the destination OTN device on the basis of the received delay request frame and the response frame comprising first time information, wherein the first time information comprises: system time T1 when the source OTN device sends the delay request frame, time T2 when the destination OTN device receives the delay request frame and system time T3 when the destination OTN device sends the response frame; upon reception of the response frame returned by the destination OTN device, acquiring, by the source OTN device, system time T4 when the source OTN device receives the response frame; and parsing, by the source OTN device, the response frame to obtain the first time information, and calculating a transmission delay between the source OTN device and the destination OTN device according to the system time T4 when the response frame is received and the first time information; wherein the generating, by the source OTN device, the delay request frame when receiving the delay measurement request sent by the user comprises: generating, by the source OTN device, a delay request message when receiving the delay measurement request sent by the user; and filling, by the source OTN device, the delay request message into Optical Channel Payload Unit k, OPUk, of an OTN frame to generate the delay request frame. generating, by the source OTN device, a delay request message when receiving the delay measurement request sent by the user; and filling, by the source OTN device, the delay request message into Optical Channel Payload Unit k, OPUk, of an OTN frame to generate the delay request frame.