The embodiment of the invention provides a video data coding method, a video data decoding method, a video data transcoding method and devices. The data coding method comprises the steps of determining a first strip set and a second strip set in a current frame, and for each first strip in the first strip set, coding each first strip based on the starting position and the ending position of each first strip; for each second strip in the second strip set, coding each second strip based on the starting position and the ending position of each second strip, wherein when the current frame needs a reference frame, the position of a reference block of a macro block in each second strip of the current frame is located in a region which is occupied by the second strips in the second strip set of the reference frame; and recording the strip serial number of each coded first strip or each coded second strip in a user-defined field of code stream data of the current frame. Partial transcoding is only required when video content is added, deleted and modified in a video coding or transcoding process, the processing speed is improved and the quality loss caused by transcoding is reduced.