Embodiments of the present application provide a method for decoding a video and an apparatus for decoding a video, which increases accuracy of data processing while simplifying a micro architecture design of inverse discrete cosine transform in video decoding process. The method comprises: storing received data to be decoded in a plurality of first data registers and a plurality of second data registers that are spaced with each other in sequence; performing shift and look-up table processing on the data to be decoded that is stored in the first data registers and the second data register, to obtain a look-up table result corresponding to a first coefficient matrix and a look-up table result corresponding to a second coefficient matrix respectively; performing a distributed computing on the look-up table result corresponding to the first coefficient matrix and the look-up table result corresponding to the second coefficient matrix, to obtain decoded data.