A method and apparatus of video coding for a video encoding system or video decoding system are disclosed. According to one method, the current block region is partitioned into one or more leaf blocks using quadtree (QT) partition and/or 1D (one-dimensional) partition by firstly signalling or parsing a first syntax element to indicate whether the current block region is split into multiple smaller blocks. According to a second method, a target syntax model from multiple syntax models is determined. The current block region is partitioned into one or more leaf blocks using QT partition and/or 1D partition and signalling block partition information according to the target syntax model at an encoder side, or the block partition information is parsed according to the target syntax model and the current block region is partitioned into one or more leaf blocks at a decoder side.