Abstract: A connecting assembly for horizontal boards and wall boards of a cabinet. Each of the horizontal boards and wall boards is formed with clamping channels along lateral sides. The connecting assembly comprises upper T-blocks, lateral T-blocks, inner cross-blocks and L-shaped corner blocks each of which is formed by a vertical slat and at least one horizontal slat. One edge of the vertical slat is formed with shallow or deep dovetail notches at equal intervals. The dovetail notches have reversely inclined faces which are interlaced, or have inclined faces. The horizontal slat has corresponding dovetail tenons spaced from each other by a distance equal to or double that of the dovetail notches.