The invention provides a method and a system for realizing ultra-low latency encoding, decoding and transmission of a high-definition video. The method comprises the steps that: an encoder receives the high-definition video, segments each frame of images constituting the high-definition video into a plurality of cut frames, and completes caching, compressed encoding and uploading in sequence by regarding each of the cut frames as a unit one by one; an Ethernet transmits compressed encoded data of the cut frames; and a decoder receives the compressed encoded data of the cut frames, completes caching and independent decoding in sequence by regarding each of the cut frames as a unit, and splices the images after independent decoding to complete the restoration of each frame of the images. Themethod and the system solve the problem that high real-time video transmission application cannot be satisfied because the existing encoding and decoding system cannot cut flexibly and is difficult to adjust and optimize, realize the effect that the total time delay from encoding, transmission to decoding is less than 50 ms, and can meet the low latency requirements of the high real-time application.