In VTM-5.0 de-block filtering for chroma component is performed at edges on 8x8 chroma sample grid except edges where chroma block is splitted by sub-block prediction mode. In this proposal, de-block filtering with 4x4 chroma sample grid is investigated for chroma component and chroma filtering is allowed for more edges which come from subblock predicted mode and also edges whose boundary strength are not equal to 0. The proposed method shows negligible bd-rate change and decoding time as shown in Table 1.