An image rendering method includes the following steps. Firstly, a source image is provided. Then, raster operations (ROPs) are performed on the source image by a first bit operating engine to obtain ROP values, and the source image are divided into at least one first region and at least one second region. Then, a first operation is performed on the first region by the first bit operating engine and a render process is executed, thereby generating first bit image data. Then, a second operation is performed on the second region by a second bit operating engine and a render process is executed, thereby generating second bit image data. Afterwards, the second bit image data of the second region are converted into first bit image data of the second region according to a screening table between the first bit operating engine and the second bit operating engine.