Abstract: H.264/AVC is the newest video coding standard with high compression efficiency.But it will take a long time to code with extremely complex algorithm，it can not achieve real-time application.In this paper，according to the characteristic of intra-frame prediction algorithm，a fast adaptive thresholds algorithm based on MAD is proposed.This algorithm will predict every macro block before coding，then select between intra 4×4（I4） and intra16×16（I16） prediction modes according to the adaptive thresholds.Then，in I4 prediction modes，select the best mode from its nine prediction modes according to the threshold. Therefore，the complexity of algorithm and coding time are reduced dramatically.Experimental results show that the coding time of proposed algorithm is reduced average by 61.3%，with a little bit increase，and the PSNR is invariable.