The present invention provides a multi-level bidirectional motion estimation method and device searching for matched blocks in a current frame and a previous frame respectively by using M1×M1 blocks of a to-be-interpolated frame as a mirror center, where the first to-be-determined matched block pair is a pair of matched blocks with a minimum sum of binary absolute difference SHAD value among all pairs of matched blocks searched out in the current frame and the previous frame; and if determined that the SHAD value of the first to-be-determined matched block pair is greater than or equal to an SHAD threshold, splitting the M1×M1 blocks into M2×M2 blocks, and searching for matched blocks again in the current frame and the previous frame respectively by using the M2×M2 blocks of the to-be-interpolated frame as a mirror center. Therefore, accuracy of motion estimation can be improved effectively, and image quality can be improved.