A method and apparatus for chroma intra prediction based on reconstructed luma pixels and chroma pixels are disclosed. The chroma intra prediction is based on a linear model of derived co-located current luma pixels of the current luma block scaled by a scaling factor. The scaling factor comprises a product term of a division factor and a scaled covariance-like value associated with neighboring reconstructed luma and chroma pixels of a current block. The division factor is related to a first data range divided with rounding by a scaled variance-like value associated with the neighboring reconstructed luma pixels of the current block. The scaled covariance-like value, the first data range, or both of the scaled covariance-like value and the first data range are dependent on the internal bit depth, with which the chroma signal is processed during video coding process, according to an embodiment of the present invention.