A method and apparatus for video coding including an IntraBC (Intra-block copy) mode with flipping for prediction unit (PU) with a non-2N×2N partition size is disclosed. An IntraBC mode is selected from a mode group comprising a normal IntraBC mode and a flipping mode for a current PU with a current PU size belonging to a size group including at least one PU size selected from 2N×N, N×2N and N×N and N is a positive integer. When the IntraBC mode is used for the current PU, a flipping flag is signaled in a current PU-level syntax to indicate whether the current PU is coded using the flipping mode. Furthermore, when the current PU is coded using the flipping mode, a flip-direction flag is signaled in the current PU-level syntax to indicate a flipping direction of a corresponding flipped reference block.