As an efficient error resilient tool in H.264, FMO (Flexible Macroblock Ordering) still has 2 disadvantages: (1) unacceptable bitrate overhead, and (2) unsuitable for widely used UEP (unequal, error protected) transmission. In this paper, to overcome these 2 disadvantages, a dynamic FMO classification (DFMOC) is proposed. For disadvantage(1), in DFMOC since lots of MBs in the same slice are placed together, thus the borate overhead is smaller. For disadvantage(2), DFMOC generates 2 slices and each of them takes unequal priority in transmission by the large and small, motion area extraction. After employing LDPC coding for UEP transmission strategy, experiment shows DFMOC has a better error robustness while still, keeps less bitrate overhead compared with traditional FMO mode: the PSNR has 1 to 2 db outperforming and the bitrate overhead keeps no more than 5% which is about a half of traditional FMO overhead.