A method for detecting image delay, characterized in that, the method is applied in a system for detecting image delay, the system comprises: an image obtaining device, an image processing device, and the method comprises: displaying, by the image processing device, any one of image frames in an incoming data stream and analyzing a data packet for image delay detection of the displayed image frame; and obtaining, by the image processing device, a detected image delay T delay of the displayed image frame, according to a reference global time T and current display time T display of the displayed image frame, wherein the reference global time T is a time at which the displayed image frame is collected by the image obtaining device and the reference global time T is encapsulated in the data packet (S 102), wherein the reference global time T is determined by: according to an image delay detection message received from the image processing device, recording, by the image obtaining device, identification information in the message and time T d of current detection indicated by the message, and recording time t d when the image delay detection message is received by the image obtaining device; wherein, collection time t c of the image frame representing a time for starting to collect the image frame is recorded, with the time t d when the image delay detection message is received as a basis; wherein, the collection time t c of the image frame is later than the time t d when the image delay detection message is received; recording, by the image obtaining device, the collection time t c of the image frame representing a time for starting to collect the image frame, according to the image delay detection message, and sending to the image processing device, according to the identification information, a collection notification message representing that the collecting of the image frame is started; and determining, by the image obtaining device, the reference global time T, according to the time T d of current detection in the image delay detection message, the time t d when the image delay detection message is received and the collection time t c of the image frame. displaying, by the image processing device, any one of image frames in an incoming data stream and analyzing a data packet for image delay detection of the displayed image frame; and obtaining, by the image processing device, a detected image delay T delay of the displayed image frame, according to a reference global time T and current display time T display of the displayed image frame, wherein the reference global time T is a time at which the displayed image frame is collected by the image obtaining device and the reference global time T is encapsulated in the data packet (S 102), wherein the reference global time T is determined by: according to an image delay detection message received from the image processing device, recording, by the image obtaining device, identification information in the message and time T d of current detection indicated by the message, and recording time t d when the image delay detection message is received by the image obtaining device; wherein, collection time t c of the image frame representing a time for starting to collect the image frame is recorded, with the time t d when the image delay detection message is received as a basis; wherein, the collection time t c of the image frame is later than the time t d when the image delay detection message is received; recording, by the image obtaining device, the collection time t c of the image frame representing a time for starting to collect the image frame, according to the image delay detection message, and sending to the image processing device, according to the identification information, a collection notification message representing that the collecting of the image frame is started; and determining, by the image obtaining device, the reference global time T, according to the time T d of current detection in the image delay detection message, the time t d when the image delay detection message is received and the collection time t c of the image frame. according to an image delay detection message received from the image processing device, recording, by the image obtaining device, identification information in the message and time T d of current detection indicated by the message, and recording time t d when the image delay detection message is received by the image obtaining device; wherein, collection time t c of the image frame representing a time for starting to collect the image frame is recorded, with the time t d when the image delay detection message is received as a basis; wherein, the collection time t c of the image frame is later than the time t d when the image delay detection message is received; recording, by the image obtaining device, the collection time t c of the image frame representing a time for starting to collect the image frame, according to the image delay detection message, and sending to the image processing device, according to the identification information, a collection notification message representing that the collecting of the image frame is started; and determining, by the image obtaining device, the reference global time T, according to the time T d of current detection in the image delay detection message, the time t d when the image delay detection message is received and the collection time t c of the image frame.