The invention discloses a frame coding and decoding method, device and system. The method comprises the steps: collecting any one image frame from a to-be-transmitted video, and determining that the image frame as a to-be-matched image frame; judging whether each block of the to-be-matched image frame is the same as the block at the same position of a preset reference image frame or not; classifying the blocks of the to-be-matched image frame according to the judgment result; and coding the classified blocks in different modes. The method solves technical problems in the related technologies that the coding and coding of all blocks in the image frame of a screen video in the same mode causes the high complexity of a coding and decoding algorithm and high code rate.