An image processing circuit and a ringing artifact removing method thereof are provided. The image processing circuit includes a deRing detection unit and a deRing filtering unit. The deRing detection unit receives a plurality of display data of an input frame and calculates a regulating reference value corresponding to each display data according to the display data and the display data at adjacent display positions. The deRing filtering unit is coupled to the deRing detection unit. The deRing filtering unit receives the display data and regulates the display data according the regulating reference values respectively corresponding to the display data to output a plurality of regulated display data.