The present invention provides a noise reduction method for use in reducing noise of a digital image, the method comprising steps of: defining a target window on a coordinate plane defined by the first chrominance and the second chrominance as the horizontal axis and the vertical axis; determining a noise threshold value according to whether an input pixel having a first chrominance value and a second chrominance value is located inside the window; determining whether the input pixel is a noise point according to the noise threshold value and luminance values of neighboring pixels of the input pixel; and adjusting the luminance value of the input pixel if the input pixel is determined a noise point. Using the noise reduction method of the present invention, not only noise of a digital image can be identified, but also the degradation caused by the noise can be reduced and thus the overall picture quality can be improved.