A method for motion vector de-interlacing decodes macro blocks in a picture, calculates motion vectors of the each MB, produces de-interlacing flag according to the threshold, realizes a Temporal Extension action and performs a Devour action. The Temporal Extension action checks multiple flag buffers, determines if a de-interlace flag should be set as WEAVE or BOB2 based on whether there exists a predetermined number of BOB flags in those flag buffers The Devour action determines if the de-interlace flag is BOB. If positive, it calculates the amount of BOB data within a predetermined area around the current MB, determines if the result is smaller than the BOB threshold and sets the de-interlace flag as WEAVE. Otherwise, it calculates the amount of the WEAVE data, determines if the result is smaller than the WEAVE threshold and sets the de-interlace flag as BOB2.