Provided herein is an image-sensing device and a method for auto white balance. An image signal processor is used to perform the method. In the method, an RGBIr photo sensor receives an image with data over red, green and blue channels. The image data over the red, green and blue channel is firstly restored. A series of weights are calculated according to the image data over an infrared channel. The weights are allocated to the image data so as to adjust the infrared ratios over the red, green and blue channels for reducing infrared effect on auto white balance. After that, an infrared weighting calculation is performed for adjusting the infrared values over the red, green and blue channels of the image. A set of white balance gains are obtained. An auto white balance is performed for obtaining a new image with infrared crosstalk compensation.