An accelerative noise filtering method for image data is provided. The present invention includes selecting four neighboring pixels around a target pixel in a pattern of a cross shape or X shape, and calculating the absolute value of a difference between the target pixel and each of the four neighboring pixels. When the absolute value of the difference of the neighboring pixel is not larger than a standard deviation, a binary value of a bit corresponding to the neighboring pixel is set "1". When the absolute value of the difference of the neighboring pixel is larger than a standard deviation, a binary value of a bit corresponding to the neighboring pixel is set "0". Consequently, a 4-bit mapping table including the binary values of the four neighboring pixels is obtained. Then, a new pixel value for replacing the target pixel value is calculated based on a calculation derived from the 4-bit mapping table.