A method of coding a moving picture reduces blocking artifacts. The method includes defining pixel sets S0, S1, S2 around a block boundary, selectively determining a deblocking mode as a default mode or a DC offset mode depending on the degree of blocking artifacts. If the default mode is selected, frequency information is obtained around the block boundary per pixel using a 4-point DCT kernel, for example, a magnitude of a discontinuous component belonging to the block boundary is replaced with a minimum magnitude of discontinuous components belonging to the surroundings of the block boundary in the frequency domain and the replacing step is applied to the spatial domain. If the DC offset mode is selected and a determination is made to perform DC offset mode, the blocking artifacts in a smooth region are removed in the DC offset mode.