The invention provides a method for high-performance video interframe coding based on time domain relevance and a transcoder thereof. The method mainly comprises coding mode division and prediction mode selection. In the coding mode division, by comparing a current frame with a last frame through a frame difference mode, movement characteristics of a current coding block are obtained, CU division is performed in advance; and in prediction mode selection, PU prediction modes under the determined CU depth are traversed. According to the method, condition judgment is performed according to the gray value difference between the current coding block and a reference block, coding depth information of a current coding unit is determined in advance before coding, interframe prediction coding times is reduced, and accordingly computation complexity at the coding end is effectively reduced. Experimental results show that on the conditions that the coding efficiency loss and the peak signal to noise ratio (PSNR) loss are very small, compared with an interframe prediction method in the HM9.0 standard, the method greatly reduces coding time.