A method for generating a pixel filtering boundary required by the auto white balance (AWB) calibration is proposed. The method includes: taking a specific color temperature reference point as a center and dividing a G/B-G/R color space into six color regions having different color component relationships; based on a saturation calculating approach of a HSV color space, respectively identifying six color boundaries in the six color regions to generate a specific hexagonal filtering boundary, so that each color boundary has a predetermined saturation difference with the specific color temperature reference point; adopting the approach for generating the specific hexagonal filtering boundary to respectively identify multiple hexagonal filtering boundaries corresponding to other color temperature reference points; generating an enveloping boundary as a pixel filtering boundary based on the specific hexagonal filtering boundary and the multiple hexagonal filtering boundaries.