A low-complexity inverse transform computation method, comprising following steps: firstly, analyzing an end-of-block (EOB) point in a matrix of a block; next, determining whether a bottom-left corner coefficient or a top-right coefficient before said EOB point is zero, and if it is zero, reducing further size of said matrix; then, determining an adequate operation mode to reduce computational complexity; and finally, realizing 2-D inverse transform through simplified 1-D inverse transforms. An inverse transform process of said method mentioned above is capable of lowering computation amount, reducing burden and computational complexity of a decompression system, and shortening effectively computation time of said 2-D inverse transform, such that it is applicable to inverse transforms of various video and still image codecs.