Abstract: In order to reduce the decision complexity of the macroblock coding mode in H.264, a fast intermode coding algorithm is proposed using the algorithm of three splitting for coding modes based on sums of absolute difference and rate-distortion value. The effectiveness of the algorithm is testified based on a testing model JM86 with H.264/AVC. The results showed that not only can it efficiently save the coding time but it also maintains similar picture quality and compression ratio.