1. An intra prediction method for a luma block of a video, comprising: calculating a sum of every two adjacent neighbor pixels X, Y in a plurality of neighbor pixels of the luma block plus 1, so as to get a first-type intermediate value, and then shifting the first-type intermediate value rightwards for 1 bit to get a first-type prediction value corresponding to the adjacent neighbor pixels X, Y; calculating a sum of the first-type intermediate value corresponding to the first two adjacent neighbor pixels X, Y and the first-type intermediate value corresponding to the last two adjacent neighbor pixels Y, Z of every three adjacent neighbor pixels X, Y, and Z in the plurality of neighbor pixels of the luma block, so as to get a second-type intermediate value, and then shifting the second-type intermediate value rightwards for 2 bits to get a second-type prediction value corresponding to the adjacent neighbor pixels X, Y, Z, wherein X, Y, Z are integers; and comparing the neighbor pixels contained in a plurality of prediction equations of the prediction modes, so as to find out the first-type prediction value or the second-type prediction value corresponding to the pixels in the luma block under the prediction modes respectively.