A monochromic image processing system and method for background removal according to dynamic data firstly obtain pixel histogram data in part of an image during a photo/text separation process. Afterwards, look-up tables for executing a background removal process are generated immediately to remove background noise of all images simultaneously. This method can solve the problem that in the multi-source document copy mode the background noise of all images cannot be removed at the same time in the prior art. It also increases the flexibility in the background removal process in various copy modes.