1. A method for calculating direct mode motion vectors of a B (Bi-predictive) picture in a moving picture coding system to extract the direct mode motion vectors of the B picture, comprising the step of selecting any one of motion vectors of a co-located block in a list 1 reference picture for direct mode as a motion vector for derivation of said direct mode motion vectors regardless of modes (a list 0 mode and/or a list 1 mode) of said motion vectors of said co-located block, determining a reference picture pointed by the selected motion vector as a list 0 reference picture for said direct mode, and calculating said direct mode motion vectors of said B picture.