To reduce the computational complexity of scalable video coding(SVC),a novel fast mode decision algorithm for H.264 scalable video coding is proposed.First,according to the analysis of mode occurrence frequency and conditional probability,the frequently occurred modes were examined at priority.If both the local-optimal condition and the monotony of rate-distortion cost condition were satisfied,the mode search process was terminated.Moreover,the candidate modes were selected based on the inter-layer mode correlation and the not suitable modes were eliminated.Comparing with the full mode search method,the proposed method accelerates the coding speed remarkably with negligible loss of quality and bit-rate.