Abstract: By analyzing the intra prediction coding characteristics of HD video sequences，a conclusion that forbidding Intra4×4 mode and using Intra8×8 and Intra16×16 modes in luma prediction can increase the coding rate significantly with almost no bit rate increase and SNR degradation is reached.Based on the conclusion，a new and fast intra prediction algorithm is proposed.This algorithm decreases the computational complexity apparently by importing a pre-decision which chooses a prediction mode between Intra8×8 and Intra16×16 before intra prediction.Experimental results show that the proposed algorithm can increase 27.8% on average of the total encoding rate，with a slight increase in bit rate and a negligible SNR drop.