The invention discloses a self-adaptive motion estimating method supporting a frame field. The problem in the prior art that the realization difficulty of hardware is large is mainly solved. The method comprises the following steps of: dividing a video sequence into N macro block pairs in a size of a 32-line 16-row pixel, and performing a two-way design of carrying out coarse motion estimation and fine motion estimation on each macro block pair; when the coarse motion estimation is carried out, respectively determining upper macro blocks and lower macro blocks of the macro block pairs in a frame field mode, dividing each macro block into eight sub-blocks, carrying out transverse 4: 1 sampling on a source macro block and a reference macro block, and then determining an optimal motion vector type and an optimal matching position in the frame field mode, and determining the frame field mode adopted by the macro block pairs; and when the fine motion estimation is carried out, according toa result of the coarse motion estimation, determining optimal matching positions of integral pixel precision, half pixel precision and 1/4 pixel precision, so as to obtain a motion estimation result of the 1/4 pixel precision. By using the method, the realization difficulty of the hardware is decreased, and the processing capacity of H.264 video encoding is improved.