A method of decoding an intra prediction mode, comprising: reconstructing an intra prediction mode group indicator and a prediction mode index, wherein the intra prediction mode group indicator indicates whether an intra prediction mode of a current block belongs to a MPM group having three intra prediction modes or a group other than the MPM group, and the prediction mode index indicates a specific intra prediction mode in the MPM group or the group other than the MPM group; constructing the MPM group using available intra prediction modes of left and top blocks of the current block; determining an intra prediction mode of the MPM group corresponding to the prediction mode index as the intra prediction mode of the current block when the intra prediction mode group indicator indicates the MPM group; and determining the intra prediction mode of the current block using the prediction mode index and the three intra prediction modes of the MPM group when the intra prediction mode group indicator does not indicate the MPM group; wherein when the intra prediction modes of the left and top blocks are equal to each other and the intra prediction mode of the left block is one of the directional intra prediction modes, the MPM group includes the intra prediction mode of the left block and two directional intra prediction modes, wherein when only one of the intra prediction modes of the left and top blocks of the current block is valid, two additional intra prediction modes are included in the MPM group and the two additional intra prediction modes are determined based on the available intra prediction mode, characterised in that when the intra prediction modes of the left and top blocks are not equal to each other and neither of the intra prediction modes of the left and top blocks is equal to the planar mode, the MPM group includes the intra prediction modes of the left and top blocks and the planar mode, and wherein the planar mode and a DC mode are two non-directional modes and a mode number of the planar mode is lower than other intra prediction modes. reconstructing an intra prediction mode group indicator and a prediction mode index, wherein the intra prediction mode group indicator indicates whether an intra prediction mode of a current block belongs to a MPM group having three intra prediction modes or a group other than the MPM group, and the prediction mode index indicates a specific intra prediction mode in the MPM group or the group other than the MPM group; constructing the MPM group using available intra prediction modes of left and top blocks of the current block; determining an intra prediction mode of the MPM group corresponding to the prediction mode index as the intra prediction mode of the current block when the intra prediction mode group indicator indicates the MPM group; and determining the intra prediction mode of the current block using the prediction mode index and the three intra prediction modes of the MPM group when the intra prediction mode group indicator does not indicate the MPM group; wherein when the intra prediction modes of the left and top blocks are equal to each other and the intra prediction mode of the left block is one of the directional intra prediction modes, the MPM group includes the intra prediction mode of the left block and two directional intra prediction modes, wherein when only one of the intra prediction modes of the left and top blocks of the current block is valid, two additional intra prediction modes are included in the MPM group and the two additional intra prediction modes are determined based on the available intra prediction mode, characterised in that when the intra prediction modes of the left and top blocks are not equal to each other and neither of the intra prediction modes of the left and top blocks is equal to the planar mode, the MPM group includes the intra prediction modes of the left and top blocks and the planar mode, and wherein the planar mode and a DC mode are two non-directional modes and a mode number of the planar mode is lower than other intra prediction modes.